v-  a        i   o 


4     -Fo.miU 


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ave 


ENUMERATION    OF    FOSSILS 


COLLECTED     IN     THK 


NIAGARA  LIMESTONE  AT  CHICAGO,  ILLINOIS; 


WITH   DESCRIPTIONS   OF   SEVERAL  NEW  SPECIES. 


BY   PROF.    ALEXANDER   WINCHELL   AND   PROF.    OLIVER   MARCY. 


WITH  TWO  LITHOGRAPHIC  PLATES. 


[FROM    THE    MEMOIRS    READ    BEFORE  THE    HOSTON    SOCIETY    OF    NATURAL   HISTORY,    VOL.    I.    NO.    I.] 


CAMBRIDGE: 

PRINTED  AT   THE    RIVERSIDE   PRESS. 
DECEMBER,   1865. 


__  Enumeration  of  Fossils  collected  in  the  Niagara  Limestone  at  Chicago,  Illinois ;  ivith  Descriptions 
of  several  New  Species.     By  Prof.  ALEXANDER  WINCHELL  and  Prof.  OLIVER  MARC  Y. 

s: 

ly*  Read  January  4th,  1865. 

JMORE  than  a  year  ago,  some  fossils  came  into  our  hands  from  the  quarries  in  the  south 
part  of  the  city  of  Chicago,  Illinois,  in  a  suburb  known  as  Bridgeport,  which  seemed  to  pos- 
sess an  unusual  degree  of  interest.  We  at  once  visited  the  place,  and  subsequently  adopted 
p  measures  to  procure  as  complete  a  collection  as  possible  of  the  fossils  of  the  locality.  Be- 
lieving that  an  exhibition  of  the  ancient  fauna  which  once  lived  upon  the  spot  would  pos- 
sess considerable  geological  interest,  we  have  made  note  of  every  species  which  has  fallen 
under  our  observation,  and,  by  an  understanding  with  Mr.  Worthen,  the  State  geologist  of 
Illinois,  offer  the  results  of  our  studies  in  the  following  paper:  — 

The  rock  at  the  principal  quarry  is  a  limestone,  which,  to  a  considerable  extent,  is  in  a 
broken  and  amorphous  condition.  The  entire  mass,  in  consequence  of  the  partial  or  com- 
plete destruction  of  the  fossils,  has  assumed  an  extremely  vesicular  structure.  The  upper 
portion  seems  to  be  somewhat  magnesian;  it  is  of  a  pale  buff  color,  more  massive  than  the 
lower,  and  contains  nearly  all  the  species  enumerated  in  the  present  paper.  Its  thickness  at 
the  quarry  is  about  eighteen  feet.  The  lower  portion  is  of  a  bluish  color,  generally  harder 
in  its  solid  parts,  but  somewhat  diversified  with  patches  of  an  argillaceous  character.  It 
has  not  been  quarried  to  any  considerable  extent,  and  the  excavations  do  not  penetrate  it  a 
greater  distance  than  about  four  feet.  It  is  only  in  this  part  that  we  find  those  interesting 
species,  Acidaspis  Ida,  Ischadites  tessellatus,  and  Gomphoceras  Marcyce.  The  whole  mass  of  the 
rock,  both  above  and  below,  is  a  congeries  of  organic  remains,  three  fourths  of  which  are 
reduced  to  an  unrecognizable  condition,  and  many  of  which  have  been  totally  or  partially 
dissolved  out,  showing,  in  some  instances,  the  delicate  tracery  of  the  exterior,  or  compli- 
cated internal  structure,  in  an  extraordinary  state  of  preservation. 

We  do  not  intend  to  be  understood  by  what  is  stated  above,  of  the  upper  and  lower 
portions  of  the  exposure,  that  in  our  opinion  we  recognize  here  the  line  of  demarcation 
between  two  stages  of  the  formation,  not  considering  our  data  sufficient  to  justify  a  con- 
clusion on  this  point. 

According  to  Mr.  Worthen,  the  rocks  at  this  locality  are  lithologically  and  paleontologi- 
cally  identifiable  with  the  Leclaire  limestone  at  the  upper  rapids  of  the  Mississippi,  near 
Leclaire,  Iowa,  and  Port  Byron,  Illinois.1  Mr.  Worthen  states  that  a  Bryozoan  form  resem- 
bling Didyonema  retiformis,  Myalina  mytiliformis,  Strophomena  depressa,  a  small  Pentamerus  re- 
sembling P.  galeatus,  and  three  or  four  species  of  chambered  shells  belonging  to  the  genera 
Orthoceras  and  Cyrtoceras,  are  common  to  the  Leclaire  and  Chicago  limestones,  establishing 
an  identity  between  the  two,  as  he  thinks  ;  while  the  Niagara  age  of  the  latter  is  shown  by 
the  number  of  Niagara  species  which  it  contains. 

Professor  Hall  (Iowa  Geol.  Rep.,  p.  73,)  had  previously  supposed  the  Leclaire  limestone 
might  be  the  western  equivalent  of  the  Gait  limestone  of  Canada  West,  though  he  subse- 
quently recognized  the  evidences  of  its  belonging  to  the  age  of  the  Niagara  group,  occu- 
pying a  position  probably  in  the  upper  part  of  the  group.2 

1  Amer.  Jour.  Sc.  and  Arts.  vol.  xxxiii.  p.  46,  1862.  a  Wiscon.  Geol.  Rep.,  pp.  67  et  seq.  and  446  el  seq. 

1 


82  WINCHELL    AND   MAECY   ON   FOSSILS   FROM   THE 

Our  own  investigations  in  the  Chicago  limestone  —  which  are  the  first  to  bring  into 
prominent  notice  this  interesting  locality — seem  to  confirm,  beyond  all  controversy,  Mr. 
Worthen's  opinion  of  the  age  of  the  rock,  as  the  following  table  will  show ;  and  by  estab- 
lishing, through  numerous  identifications,  given  below,  its  parallelism  with  the  Racine  lime- 
stone,—  admitted  to  be  equivalent  to  the  Leclaire  limestone, — it  becomes  geologically 
demonstrated  that  all  these  limestones  occupy  a  position  in  the  Niagara  group  of  New 
York. 

But  with  which  member  of  the  group  shall  they  be  synchronized  ?  Our  own  identifications 
tend  to  show  a  relationship  with  both  the  Niagara  limestone  and  the  Niagara  shale ;  of  those 
species,  however,  which,  at  the  East,  occur  in  the  Niagara  shale,  it  will  be  observed  that 
some,  as  Slrophomena  rhomboidalis,  Atrypa  relicularis,  Spirifera  crispa,  JS.  radiata,  Meristella  nitida, 
and  Rhynchonella  mglecta,  are  species  which  enjoyed  either  a  great  geological  or  great  geo- 
graphical range,  or  both  together,  and  are  thus  proved  to  have  been  wanting  in  that  sen- 
sibility to  geological  variations  which  is  requisite  in  fossils  relied  upon  for  stratigraphical 
determinations.  The  same  may  perhaps  be  said  of  Caryocrinus  ornatus  and  Lozonema  subulata. 
Of  the  others,  the  Poli/zoa  may  be  regarded  as  only  provisionally  identified.  There  is  left, 
then,  no  strong  bond  of  alliance  between  the  Chicago  limestone  and  the  Niagara  shale,  ex- 
cept the  prevalence  of  crinoidal  remains  in  both.  But  it  will  be  noticed  that  we  have  been 
unable  to  identify  any  species  except  Caryocrinus  ornatus ;  so  that,  admitting  the  alliance 
shadowed  forth  by  the  presence  of  the  crinoidal  type  in  considerable  force,  we  have  a 
much  stronger  affinity  established  with  the  Niagara  limestone  by  the  identification  of  sev- 
eral species  of  true  corals,  as  well  as  by  the  abundance  of  individuals  of  this  type.  For  the 
present,  therefore,  it  seems  to  us  that  the  Chicago,  Racine,  and  Leclaire  limestones  exhibit  a 
satisfactory  affinity  with  the  Niagara  limestone  of  New  York. 

We  have  detected  in  the  Chicago  limestone  no  less  than  eighty-two  species,  of  which 
thirty-nine  seem  to  be  hitherto  undescribed.  If  we  add  to  these  the  few  additional  species 
described  by  McChesney,  from  the  same  locality,  we  find  that  a  single  quarry  has  furnished 
not  less  than  eighty-seven  species,  —  another  evidence  of  the  abundance  and  variety  of  life 
which  teemed  in  the  paleozoic  seas. 

None  of  the  Gasteropoda  or  Cephalopoda  have  been  identified  with  New  York  species. 
Of  the  identifications  with  New  York  species,  the  corals  are  all  (except  Pctraia  calicula) 
from  the  Niagara  limestone,  and  the  mollusks  (including  Bryozoa)  are  all  from  the  Niagara 
shale. 

It  is  noticeable  that  we  do  not  find  in  our  collection  any  specimens  of  HeliolUes,  Eucalyp- 
tocrimis  decorus,  Orthis  elegantula,  Spirifera  nm/arensis,  Pentamcrus  oblongm,  Rhynchonella  cmieata, 
or  Calymene. 

Of  the  old  species  recognized  by  us,  all  have  been  described  from  the  Niagara  group  of 
North  America.  Loxonema  subulata  Conrad,  was,  however,  originally  described  from  the 
Clinton  group  of  New  York,  but  has  been  identified  in  the  Niagara  group  of  Canada  West, 
as  well  as  at  Chicago.  The  geographical  distribution  of  these  species  in  some  of  the  North- 
western States,  Canada  West,  and  Europe,  is  presented  at  a  glance  in  the  following  table : 


NIAGARA   LIMESTONE   OF    CHICAGO,   ILLINOIS. 


83 


GEOGRAPHICAL  DISTRIBUTION  OF  NIAGARA  SPECIES  IDENTIFIED  AT  CHICAGO. 


N.  Y. 

Wis. 

IND. 

CAN. 

KUR. 

* 
* 
* 

* 

* 

Dipliyphyllum  ctespitosum  Hall  sp  

Favosites  gothlandica  Lam  

* 
* 
* 
* 

"         reticulata  Hall  

» 
* 
* 
* 

* 

* 
* 
« 
* 
* 

* 

* 
* 
* 

* 

* 

* 

* 

* 

* 

* 

* 
* 

* 

• 

* 
* 

* 

"      nodostriata  Hall  

Meristella  nitida  Hall  sp  

Rliynchonella  neMecta  Hall  

* 

* 
* 
• 
* 
* 

* 
* 

* 

* 

* 

*  Pterinea  ne^lecta  McChesney  sp  

Ambonychia  mytiloidea  Hall  

Pleurotomaria  Halei  Hall  

"             Hoyi  Hall  

Loxonema  subulata  Con  

*  Orthoceras  Laphami  McChenesy  

Cyrtoceras  Foster!  Hall  

ENUMERATION  OF  SPECIES. 

Petraia  calicula  Hall  sp.,  Pal.  N.  Y.,  ii.  p.  Ill,  pi.  xxxii.  fig.  1,  a-Jc. 

Zaphrentis  turbinatus  Hall  sp.,  Pal.  N.  Y.,  ii.  p.  112,  pi.  xxxii.  fig.  2. 

Cysiipliyllum         sp  ?     A  fragment  generically  well  marked. 

Diphyphyllum  ccespitosiim  Hall  sp.,  Pal.  N.  Y.,  ii.  p.  116,  pi.  xxxiii.  fig.  1,  a-b. 

Favosites  gothlandica  Lam.  (F.  niagarensis  Hall.)  We  adopt  the  suggestion  of  Billings 
(Canad.  Journal,  March,  1859,  p.  99),  in  referring  this  form  back  to  the  original  species.  It 
occurs  abundantly  in  the  upper  part  of  the  quarry. 

Favosites  venustus  ?  Hall  sp.,  Pal.  N.  Y.,  ii.  p.  120,  pi.  xxxiv.  fig.  1,  a  -  i. 

The  agreement  is  not  striking.  This  is  an  expanded,  incrusting  coral,  adapting  itself  to 
the  inequalities  of  the  underlying  surface,  and,  in  places,  developing  tubercular  masses. 
The  tubes  are  ordinarily  not  more  than  an  eighth  of  an  inch  long,  but,  in  the  tubercles 
become  sometimes  half  an  inch  in  length.  In  the  tuberculous  parts,  the  diaphragms  are 
seen  to  be  direct  and  crowded.  No  indications  of  a  radial  system  are  seen.  The  cell- 
mouths  are  conformable  to  this  species.  The  Chicago  fossil  bears  considerable  resemblance 
to  Thecostcgites  hemisphcericus  Rom.  (Sil.  Fauna  des  Westl.  Tenn.  Taf.  ii.  fig.  3). 

*  These  species  are  not  enumerated  by  Hall  among  the  fossils  of  Wisconsin. 


84  WINCHELL   AND   MARCY   ON   FOSSILS    FROM   THE 

CLADOPORA  Hall. 

Cladopora  lichenoides  W.  and  M. 
Plate  II.  figure  1. 

Polypary  consisting  of  a  mass  of  crowded  cylindrical  tubes  arranged  in  ramose  and  folia- 
ceous  forms,  both  forms  being  sometimes  united  in  one  specimen.  The  earlier  growth,  in 
one  of  our  specimens,  is  explanate.  The  cells  are  elongated,  obliquely  horizontal,  crowded, 
overlapping,  with  their  mouths  opening  obliquely  through  the  epitheca.  The  frond  devel- 
ops into  an  irregularly  undulate  form,  sometimes  dividing,  and  some  of  the  lobes  bending 
round  laterally,  after  the  manner  of  one  or  two  turns  of  an  Archimedes.  From  the  border  of 
the  frond  arise  terete,  bifurcating  branches,  with  the  mouths  opening  on  all  sides.  All  the 
cell-mouths  are  somewhat  crescentiform,  the  outer  lip  often  slightly  indented,  and  some- 
times sufficiently  so  to  give  the  mouth  a  triangular  outline. 

In  exfoliated,  weathered  specimens,  the  cells  are  seen  to  be  cylindrical  and  separately 
walled,  but  closely  in  contact.  The  width  of  three  of  these  cells  occupies  the  space  of  one 
tenth  of  an  inch ;  their  length  is  about  a  third  of  an  inch.  No  evidences  of  septa  or  la- 
mellse  can  be  detected. 

The  cell-mouths  of  this  abundant  and  beautiful  species  resemble  Ccenites,  Alveolttes,  and 
Cladopora.  The  fossil  differs  from  Ccenites  and  Cladopora  in  not  having  a  solid  coenenchyma, 
and — at  least  from  the  usual  forms — in  its  foliaceous  ememble.  It  differs  from  Alveolites  in 
the  want  of  intra-cellular  structure.  Some  species  of  Cladopora  figured  by  Hall,  however, 
exhibit  generic  characters  to  which  the  present  species  is  sufficiently  conformable. 

Cladopora  verticillata  W.  and  M. 
Plate  II.  figure  2. 

Corallum  arising  in  the  form  of  a  stem,  from  which  spreads  out,  horizontally,  in  all  direc- 
tions, a  thin  and  delicate  frond,  composed  of  small  radiating  cells  continually  multiplying 
in  number  with  the  distance  from  the  axis.  This  circular  frond  is  covered  superiorly  by 
an  epitheca  through  which  the  cell-mouths  open  as  in  other  species.  The  mouths  are  tri- 
angular-crescentic  ;  the  cells  show  traces  of  dissepiments.  At  the  height  of  an  inch  and  a 
half  above  the  first  frond  is  another,  in  all  respects  similar,  and  a  cylindrical  perforation 
runs  through  the  rock  from  one  to  the  other.  This  structure  has  been  seen  in  two  unmis- 
takable specimens.  It  seems  probable  that  other  verticils  or  circular  fronds  occur  between 
the  two  observed,  and  that  the  whole  space  was  originally  filled  up  with  verticils  of  cells 
alternating  with  plates  of  epitheca ;  but  of  this  we  have  no  other  evidence  than  the  porous 
condition  of  the  rock,  with  occasional  traces  of  minute  coral  tubes. 

In  the  specimen  which  is  the  subject  of  this  description,  a  second  stem,  smaller  than  the 
first,  is  seen  perforating  the  rock  for  the  depth  of  half  an  inch,  and  sending  out  a  verticil 
which  becomes  confluent  with  that  of  the  larger  specimen.  Is  this  a  new  colony  rooted, 
banyan-like,  from  the  branches  of  a  parent  ? 

The  axis  in  our  specimens  is  hollow.  The  filling  is  a  calcareous  clay,  showing  no  other 
structure  than  a  slight  porousness,  with  obscure  vertical  striations  on  the  exterior.  We 


NIAGARA  LIMESTONE   OF   CHICAGO,  ILLINOIS.  85 

might  be  permitted  to  infer,  from  analogy,  that  the  original  axis  was  solid,  and  resembled 
the  cylindrical  stems  of  other  species  of  the  genus,  but  has  been  destroyed  in  our 
specimens. 

Diameter  of  the  hollow  axis,  .16  below,  .19  above ;  diameter  of  verticils,  more  than  three 
inches ;  number  of  cells  in  one  tenth  of  an  inch,  6  to  8. 

Much  remains  to  be  learned  of  this  coral ;  and  we  desire  to  direct  attention  to  it  by 
making  known,  in  the  mean  time,  its  very  extraordinary  ensemble.  The  two  species  of 
Cladopora  described  by  us  not  only  present  unique  characters  in  their  general  forms,  but, 
in  their  structure,  furnish  us  with  the  proofs  that  Cladopora  is  a  generic  type  founded  in 
nature. 

Cladopora  fibrosa  Hall.     Pal.  N.  Y.,  II.  139,  pi.  xxxviii.  figs.  4,  5. 

Cladopora  seriata  Hall.     Pal.  N.  Y.,  II.  137,  pi.  xxxviii.  fig.  1. 

Cladopora  reticulata  Hall.  Pal.  N.  Y.,  H.  141,  pi.  xxxix.  fig.  3.  We  have  specimens  of 
this  exhibiting  the  reticulations  spread  over  a  surface  eight  or  ten  inches  square. 

Halysites  catenularia  Linn.  sp.  Seldom  found  in  a  recognizable  state  of  preservation.  We 
occasionally  find  casts  of  the  spaces  enclosed  by  the  labyrinthine  walls,  which,  with  the 
vertical  striations  and  transverse  wrinkles  of  the  tubes  preserved,  present  an  object  closely 
resembling  the  enigmatical  fossil  named  Cophinus  diibius  in  the  Silurian  System,  (pi.  xxvi.  fig. 
12,)  and  which  in  the  Siluria  (p.  136,  and  pi.  xv.  fig.  4)  is  attributed  to  the  slow  gyration  of 
the  stems  of  encrinites  after  the  mud  had  settled  around  them.  The  Ludlow  fossil  may  clear- 
ly have  had  the  origin  attributed  to  it;  but  our  specimens,  though  at  first  obscure,  have 
furnished,  at  length,  conclusive  evidence  of  being  the  impressions  or  casts  of  the  walls  of  a 
Halt/sites.  The  transverse  dissepiments  in  some  of  the  cells  are  well  preserved  and  numerous. 

Siromatopora  sp  ?  We  have  a  weathered  specimen,  exposing  the  stellately  diverging 
ramulets  formed  in  the  interlaminar  spaces.  This  curious  organism  would  not  ordinarily 
be  identified  as  a  Stromatopora  ;  but,  by  the  aid  of  Dr.  Rominger's  extensive  suite  of  specimens 
of  this  genus,  its  true  character  becomes  apparent.  There  is  a  specimen  of  the  type,  which 
shows  stellate  cell-mouths,  in  the  Illinois  State  Cabinet.  This  is  in  the  usual  state  of  pres- 
ervation, and  may  be  identical  with  ours,  though  we  have  only  had  the  opportunity  to  give 
it  a  hasty  glance. 

Stictoporapunctipora?  Hall.     Pal.  N.  Y.,  II.  157,  pi.  xl.  B,  fig.  2  a-c. 

Polypora  incepta  ?  Hall.  Pal.  N.  Y.,II.  167,  pl.xl.  D,fig.  5  «-/.  A  large  undulately  cyathi- 
form  frond,  nearly  six  inches  in  diameter,  with  fenestrules  somewhat  smaller  than  in  the 
typical  species.  The  cells  have  not  been  certainly  distinguished  either  in  this  or  the  fol- 
lowing species. 

Fenestella  elegans?  Hall.     Pal.  N.  Y.,  II.  164,  pi.  xl.  D,  fig.  1  a-g. 

Lwhenalia  concentrica  Hall.     Pal.  N.  Y.,  II.  171,  pi.  xl.  E,  fig.  5,  a-g. 

ISCHADITES  Murchison. 

Ischadites  tessellatus  W.  and  M. 

Plate  II.  figure  3. 

Body  somewhat  tapering,  pyriform,  compressed  on  the  side  toward  which  the  smaller  end 
is  slightly  inflected  ;  the  larger  end  imperfect  in  all  our  specimens.  One  example  is  some- 
what in  the  form  of  a  triangular  prism  with  rounded  edges,  and  the  sides  indented  toward 


86  WINCHELL  AND  MARCY   ON    FOSSILS   FROM   THE 

the  base,  while  the  upper  end  is  convex.  The  whole  exterior  is  divided  into  small  rhomboidal 
or  nearly  square  areas  by  ridges  which  originate  at  the  apex  and  describe  curves  obliquely 
approaching  the  base,  and  crossing  each  other  like  the  curves  of  the  "  engine-turned 
ornament  of  a  watch."  In  the  best  preserved  specimens,  these  ridges  are  surmounted  by 
little  crests  deepening  the  pits  or  cells  which  they  mark  out.  In  other  specimens  these 
cells  are  simply  hopper-shaped  cavities.  The  cells  of  course  increase  in  size  from  the  ori- 
gin of  the  ridges  to  that  part  of  the  surface  where  the  diameter  of  the  body  is  great- 
est. In  the  bottom  of  each  cell  is  a  small  pore  penetrating  the  internal  cavity.  Besides 
this,  each  cell  communicates  by  pores  with  the  four  neighboring  cells  touching  it  at  the 
angles.  These  connecting  pores  are  parallel  with  the  general  surface,  and  pass  under  the 
intersection  of  the  two  crests  or  ridges.  Each  rectangular  intersection,  therefore,  rests  over 
the  crossing  of  a  couple  of  right-angled  passage-ways.  In  some  specimens,  in  which  the 
hopper-shaped  cells  are  shallow,  these  pores,  extending  across  the  cell  from  corner  to  corner, 
present  the  appearance  of  open  passage-ways  excavated  through  the  substance  of  the  test ; 
on  the  side  toward  the  larger  end  of  the  body,  however,  the  passage-way  remains  covered. 
In  such  cases,  the  feature  which  first  strikes  the  eye  is  a  pair  of  furrows  intersecting  each 
other  at  right  angles  in  the  middle  of  each  cell,  forming  three  sides  of  a  cross. 

Our  specimens  are  all  casts,  and  exhibit  no  further  internal  structure,  except  that  the 
central  pores  can  be  seen  penetrating  the  internal  cavity,  and  losing  themselves  at  the 
depth  of  a  quarter  of  an  inch.  Polished  sections  at  right  angles  with  the  surface  present 
obscure  indications  of  sac-like  cells  extending  inward  from  the  surface  about  one  fourth 
of  an  inch.  There  is  one  of  these  on  each  side  of  the  central  pore,  and  the  inner  end 
of  the  cell  is  regularly  rounded.  The  pore  seems  to  have  been  the  means  of  communi- 
cation between  the  inner  common  cavity  of  the  body  and  the  external  element.  It  was 
perhaps  respiratory  in  its  function.  The  cells  present  the  appearance  of  individualization, 
while  the  entire  body  was  undoubtedly  a  compound  organism.  Polished  surfaces  at  right 
angles  with  the  larger  axes  of  these  cells  do  not  succeed  in  bringing  their  walls  into  view. 

No  peduncle  of  attachment  appears  to  have  been  in  connection  with  the  smaller  end  ;  but 
the  larger  ends  are  all  imperfect,  and  it  seems  not  unlikely  that  this  end  was  adherent,  or 
possibly  pedicled. 

The  largest  and  most  perfect  specimen  is  2.5  inches  in  length,  with  a  maximum  diameter 
of  1.75  inches.  The  diameter  of  the  cells  over  the  most  swollen  portion  of  the  body  is  .09 
inch. 

These  very  interesting  and  beautiful  specimens  are  evidently  congeneric,  if  not  conspecific 
with  I.  K&nigi  Murchison,1  and  I.  canadensis  Billings,  (Geol.  of  Canada,  pp.  309,  327,)  though 
the  entire  form  of  I.  canadensis  has  not  been  figured,  and  I.  Komigi  is  less  attenuate  at  the 
smaller  end.  We  are  of  the  opinion,  also,  that  they  possess  close  relations  with  Dictyocrinus 
Conrad,  and  Tetragonys  Eichwald;  and  that  all  these  genera  belong  to  the  same  zoological 
type  as  Reccptaculites,  which  has  been  shown  by  Salter  to  be  one  of  the  Foraminifera,  as  D.  D. 
Owen  conjectured  in  1844.  At  least,  the  affinities  of  Ischadites  with  Receptaculites  seem  to 
be  pretty  clearly  shown  by  our  specimens ;  and  it  is  worthy  of  remark  that  Morris,  in  his 
Catalogue,  has  united  I.  Kwnigi  and  Receptaculites  Neptuni,  while  Professor  Hall  says,  (Pal. 
N.  Y.,  HI.  p.  148) :  "  The  figures  [of  I.  Kceniyi]  in  the  Silurian  System  bear  so  close  a  resem- 
blance to  Receptaculites  that  I  could  scarcely  regard  them  as  distinct  from  that  genus." 

1  Silurian  System,  697,  pi.  xxvi.  fig.  11 ;  Siluria,  pi.  xii.  fig.  6. 


NIAGARA  LIMESTONE   OF    CHICAGO,   ILLINOIS.  87 

ACTINOCRINUS  Miller.1 

Actinocrinus  obpyramidalis  W.  and  M. 

Plate  II.  figure  4. 

Body  pentangularly  obpyramidal ;  radial  series  standing  out  in  salient  angles  with 
depressions  between,  deepening  upward,  and  giving  great  prominence  to  the  arm  bases, 
which  are  quite  small,  and  exist  in  pairs.  Dome  arched,  with  the  appearance  (in  our  speci- 
mens) of  a  broken  proboscis  a  little  nearer  the  centre  than  the  anal  side. 

Basal  plates  not  seen ;  radials  three,  the  two  lower  hexagonal,  the  first  a  little  larger  than 
the  other  two,  and  having  its  upper  side  shortest ;  the  third  radial  heptagonal,  supporting  a 
pair  of  hexagonal  secondary  radials  upon  its  upper  sloping  faces.  The  other  plates  of  the 
cup  cannot  be  satisfactorily  defined  in  our  specimen.  They  give  evidence  of  having  been 
elevated  and  sculptured.  We  have  seen  a  specimen  1.75  inches  high  to  the  top  of  the  dome. 

This  species  has  all  the  general  appearance  of  an  Actinocrinus,  and  resembles  such  Carbon- 
iferous species  as  A.  quinquelobus  and  A.  cornigerus ;  and  was  not  improbably  furnished,  like 
them,  with  spines  upon  the  dome.  We  know  of  no  allied  species  of  the  same  geological 
age. 

MEGISTOCRINUS  Owen  and  Shumard. 

Megistoerinus  Marcouanus  W.  and  M. 

Plate  II.  figure  5. 


a.  Left  antero-lateral  ray.  b.  Left  postero-lateral  ray. 

c.  Azygos  side,  with  one  half  of  the  azygos  interradials. 

1  Learning,  after  we  had  engaged  in  this  investigation,  that  our  own  specimens  of  that  type  should  be  worked  up  by  him. 

Mr.  W.   H.   Niles,  of  the  Museum  of  Comparative  Zoology  He  has,  however,  insisted  on  our  proceeding  independently ; 

at  Cambridge,  was   occupied  in  a  reinvestigation  of  Crinoi-  and,  having  done  so,  we  deem  this  statement  demanded  by  the 

dea  with  a  view  to  publication,  we  should  have  preferred  that  courtesy  which  ought  to  prevail  among  co-laborers  in  science. 


88  WINCHELL   AND   MARCY   ON   FOSSILS   FROM   THE 

Body  large  and  massive,  somewhat  obconic,  spreading  more  rapidly  towards  the  arm 
bases ;  base  sub-acute,  generally  turned  to  one  side.  Basal  plates  three,  equal,  hexagonal 
— the  inner  side  very  short  —  a  little  broader  than  high.  Radials  three  in  each  series.  Of 
the  first  radials  three  stand  opposite  the  three  basals,  and  are  hexagonal,  a  little  higher  than 
wide,  the  upper  side  being  shortest,  the  lower  next  in  length.  The  other  two  first  radials 
stand  opposite  the  division  between  two  basals ;  they  are  heptagonal  by  the  division  of  the 
base,  the  two  basal  sides,  however,  lying  nearly  in  the  same  straight  line.  The  second  ra- 
dials are  hexagonal,  nearly  as  large  as  the  first,  one  fifth  longer  than  wide,  the  upper  and 
lower  sides  about  half  the  length  of  the  others.  The  third  radials  are  larger  than  the  sec- 
ond, octagonal  in  the  anterior  and  antero-lateral  rays,  having  two  upper  sides,  each  of 
which  is  about  equal  to  the  lower  one,  the  lateral  sides  being  considerably  the  longest, 
and  thus  causing  this  plate  to  be  longer  than  broad ;  in  the  postero-lateral  rays  they  are 
heptagonal  by  the  enlargement  of  the  anal  plates.  The  first  supraradial  plates  are  irreg- 
ularly heptagonal,  two  thirds  as  large  as  the  third  radial.  Second  supraradials  heptagonal  or 
octagonal,  of  the  same  size  as  the  first  or  smaller,  supporting  on  their  upper  sloping  sides  a 
pair  of  small  pentagonal  brachials.  Number  of  arms  twenty.  First  regular  interradial  hexa- 
gonal, nearly  as  large  as  the  first  radials,  supporting  on  its  shorter  upper  sides  a  pair  of 
smaller  interradials,  which  are  succeeded  by  about  ten  other  interradials,  making  thirteen 
in  all.  The  azygos,  or  anal  interradials  number  about  thirty.  The  first  rests  upon  the 
basals,  and  has  precisely  the  same  form  and  size  as  the  antero-lateral  first  radials ;  like  the 
radials,  also,  it  is  succeeded  by  two  others,  producing  a  series  resembling  the  true  rays,  dif- 
fering, however,  in  the  plates,  being  a  little  smaller  than  the  true  radials,  and  being  suc- 
ceeded by  five  other  smaller  plates  nearly  in  the  same  line.  Between  this  series  of  anals 
and  each  contiguous  ray  lies  a  series  of  three  plates  followed  by  two  pairs.  First  inter- 
supraradial  hexagonal,  surmounted  by  two  pairs  of  smaller  ones.  The  formula  of  this  spe- 
cies is,  therefore,  as  follows  :  — 

Basals 3 

Radials    3X5= 15 

Supraradials    2X2X5= 20 

Brachials  2X2X2X5= 40 

Regular  Interradials    13X4= 52 

Azygos  Interradials 30 

Inter-supraradials  5x5= 25 

Interbracbials   0 


Total  plates  in  the  cup 185 

One  of  our  specimens  is  3.4  inches  long,  to  the  bases  of  the  arms.  Another  one,  defec- 
tive below,  has  a  diameter  of  three  inches  at  the  bases  of  the  arms ;  most  of  the  specimens 
are  not  over  half  this  size. 

There  is  a  variety  of  this  species  (apparently)  which  is  marked  by  ridges  along  the 
series  of  radials  and  secondary  radials.  These  ridges  (in  casts)  are  not  interrupted  by  the 
sutures. 

This  massive  species  bears  a  remarkably  close  affinity  with  Adinocrinus  Christyi  Hall,  (No- 
tice of  Waldron  Fossils,  p.  2,)  but  it  may  be  discriminated  as  follows :  The  first  radial  has  a 
height  greater  than  its  width,  instead  of  being  equal  to  it ;  the  second  radial  is  higher  than 
wide,  instead  of  the  reverse ;  the  third  radial  is  octagonal  in  the  antero-lateral  rays,  and  is 


NIAGARA   LIMESTONE   OF    CHICAGO,   ILLINOIS. 


89 


larger  than  the  second,  instead  of  smaller ;  the  regular  interradials  are  fewer  in  number, 
instead  of  fifteen  or  over.  Lastly,  the  ridges  over  the  radial  plates  are  entirely  wanting  in 
the  typical  specimens,  and  in  the  supposed  variety  are  not  interrupted  by  the  sutures.  It 
is  quite  possible  that  the  structure  of  the  supposed  variety  may  conform  completely  to  that 
of  A.  Christi/i. 

It  will  be  observed  that  this  species  departs  from  the  usual  form  of  Megistocrinus  as  known 
in  the  Carboniferous  rocks,  at  the  same  time  that  it  falls  strictly  under  the  formula  of  that 
genus.  We  feel  constrained  to  say  that  the  same  is  true  of  Actinocrinus  Christyi  Hall,  —  a 
circumstance  which  will  enable  us  to  perpetuate  this  preoccupied  specific  name  under  the 
form  of  Megistociinus  Cliristyi. 

ICHTHYOCRINUS  Conrad. 


Ichthyocrinus  corbis  W.  and  M. 

Body  pyriform,  section  nearly  circular,  one  specimen  flattened  and 
even  indented  on  the  anal  side ;  greatest  diameter  at  one  third  the 
height  of  the  body  below  the  arm  bases;  oblique  height  gradually 
or  rather  rapidly  curved  below,  and  more  rapidly  curved  in  the 
vicinity  of  the  greatest  diameter,  giving  the  body,  in  most  specimens, 
a  sub-ventricose  appearance.  Stem  very  slender  at  the  upper  end, 
,  turned  to  one  side  in  all  our  specimens.  Basal  plates  five,  equilater- 
ally  triangular,  slightly  truncated  by  the  stem  at  their  lower  apex, 
flattened,  so  that  the  five  sutures  by  their  prominence  convert  the 
pelvic  cup  into  an  inverted  pentagonal  pyramid.  Radials  two  in  each 
ay,  alternating  with  the  basals,  which  project  their  angles  in  pairs 
into  the  lower  sides  of  the  first  radials,  rendering  them  pentagonal 
by  a  reentrant  angle  below;  second  radials  also  pentagonal,  with 
two  upper  sloping  faces  to  receive  the  secondary  radials.  Secondary 
radials  four  in  each  series,  each  with  a  transverse  diameter  equal 
to  twice  its  height  or  more;  the  fourth  with  two  upper  sloping  sides 
for  the  support  of  the  tertiary  radials,  which  are  about  nine  or  ten  in 
number  in  each  radiating  series,  gradually  diminishing  in  height 
from  below  upwards,  while  they  increase  in  transverse  diameter,  so  that  the  uppermost 
plates  are  not  more  than  one  twentieth  of  an  inch  in  vertical  height,  while  their  transverse 
dimension  is  one  fourth  of  an  inch. 

In  one  of  our  specimens  the  height  of  the  body  to  the  bases  of  the  free  arms  is  1.8  inch ; 
greatest  diameter  (.55  inch  below  the  free  arm  bases)  1.62  inch.  In  another  specimen,  less 
ventricose,  the  height  is  2  inches,  and  the  greatest  diameter  (.66  inch  below  the  free  arm 
bases)  is  1.6  inch. 

The  distinctive  characters  of  the  species  are  the  small  size  of  the  stem,  the  large  size  of 
the  basal  plates,  corresponding  to  the  sides  instead  of  the  angles  of  the  pentagonal  base, 
the  presence  of  two  instead  of  three  radials,  and  the  perfectly  straight  transverse  sutures 
separating  the  plates  of  the  several  radial  series,  except  the  suture  separating  two  succes- 
sive series. 

In  the  specimens  which  we  have  for  examination,  the  exterior  of  the  plates  is  removed, 
and  the  filling  of  the  sutures  projects  conspicuously,  giving  the  body  a  peculiar  basket-like 

3 


Ichthyocrinus  corbis. 
Showing  the  plates  of  one  ray. 


90 


WINCHELL   AND   MARCY   ON   FOSSILS   FEOM   THE 


or  net-like  appearance.  The  characters  about  the  base  are  somewhat  obscure,  and  it  is  pos- 
sible we  have  overlooked  the  real  first  radial.  This  supposition  would  reduce  the  fossil  to  a 
greater  conformity  with  I.  Icevis,  but  it  would  still  be  distinct. 

GLYPTOCRINUS  Hall. 

Glyporcinns  Carleyi  ?  Hall.  Notice  of  Waldron  Fossils,  p.  19.  We  have  several  speci- 
mens, in  a  poor  state  of  preservation,  which  evidently  belong  to  Glyptocrinus,  or  one  of  the 
allied  genera.  We  are  inclined  to  think  the  basal  plates  are  entirely  covered  by  the  stem. 
The  radials  are  three  in  each  series.  A  conspicuous  ridge  runs  along  the  middle,  bifurcate 
ing  at  each  end,  in  the  centre  of  the  first  and  third  radials.  The  lower  branches  of  the 
ridges  proceed  to  the  centre  of  the  subradials.  The  azygos  interradius  is  broader  than  the 
others,  and  contains  a  plate  with  radiating  ridges.  The  whole  number  of  interradials  can- 
not be  determined.  The  form  of  the  cvip  is  pentangularly  turbinate,  about  three  fourths 
of  an  inch  high,  with  the  same  diameter  at  the  bases  of  the  arms.  In  form,  size,  and  dis- 
position of  the  visible  markings,  our  specimens  agree  with  specimens  from  Waldron. 

Glyptocrinus  sp.  ?  A  species  quite  distinct  from  the  last,  being  more  slender,  with  a 
more  attenuate  base,  and  more  spreading  rays.  Our  specimens  also  are  of  smaller  size. 

LECANOCRINUS  Hall. 

Lecanocrinus  pusillus  W.  and  M. 

Body  small,  depressed,  broader  than  high,  constricted  above  the  first  radials.  Basals 
small,  two  hexagonal  and  one  pentagonal.  Subradials  pentagonal  and  hexagonal,  each 
equal  in  size  to  the  whole  base.  Radials  three  in  each  ray,  —  the  first  five-sided,  having 
the  upper  side  longest,  the  basal  sides  next  in  length,  and  the  remaining  two  parallel  with 
each  other;  second  radial  quadrangular,  short,  being  five  times  as  broad  as  high;  third  ra- 
dial with  two  upper  sloping  faces  supporting  a  pair  of  secondary  radials.  Secondary  radi- 
als transversely  oblong,  quadrangular ;  no  more  than  three  have  been  seen.  Height  to 
base  of  arms,  .24  inch;  diameter  at  base  of  arms,  .40  inch. 

EUCALYPTOCRINUS    Goldf. 
Eucalyptocrinus  chicagoensis  W.  and  M. 

Body  massive,  obconic  from  the  base  to  the 
arms ;  base  truncate,  deeply  impressed,  obscure- 
ly pentagonal,  the  rim  of  the  impression  pre- 
senting five  protuberances  corresponding  to  the 
intervals  between  the  first  radials.  Basal  plates 
small,  concealed  within  the  basal  cavity.  First 
radial  plates  quadrangularly  heptagonal,  the 
upper  side  presenting  an  obtusely  reentrant 
angle.  Second  radials  as  large  as  the  first, 
nearly  square,  but  having  the  lower  side  angu- 
lated  to  suit  the  reentrant  angle  of  the  first 
radial.  Third  radials  hexagonal,  or  very  nearly 
pentagonal,  the  lower  lateral  sides  being  rela- 
tively short,  and  the  upper  side  almost  zero. 
First  supraradial  smaller  than  the  third  radial, 


F.ucalyptocrinui  chicagoensis. 


NIAGARA   LIMESTONE    OF    CHICAGO,   ILLINOIS.  91 

irregularly  pentangular.  Second  supraradials  less  than  half  the  size  of  the  first,  pentangu- 
lar, with  the  lower  lateral  sides  shortest,  each  upper  side  supporting  a  small  triangular  piece, 
upon  which  rests  the  first  arm  plate.  The  interradial  plates  are  one  large  and  two  smaller 
to  each  interradius.  The  general  outline  of  the  lower  is  somewhat  kite-shaped;  it  is 
bounded  by  ten  contiguous  plates,  but  the  two  lower  lateral  sides  are  so  crowded  by  the 
bounding  second  radials,  that  the  two  lower  sides  touching  the  first  radials  are  extremely 
short ;  and  the  two  short  upper  sides,  in  contact  with  the  second  interradials,  lie  nearly  in  the 
same  line.  The  pair  of  smaller  interradials  are  nearly  as  long  and  broad,  taken  together, 
as  the  first  interradial ;  the  greatest  width  is  below  the  middle,  and  their  summits  reach 
higher  than  the  bases  of  the  arms.  The  intersupraradial  is  similar  in  shape  to  the  pair  of 
upper  interradials,  but  smaller,  and  the  lower  side  is  almost  zero,  touching  the  apex  of  the 
third  radial.  Height  of  cup  to  bases  of  arms,  1.1  inch ;  greatest  diameter  (at  arm  bases), 
1.7  inch. 

This  species  greatly  resembles  E.  crassus  Hall,  but  a  comparison  of  numerous  specimens 
of  each  shows  constant  differences.  The  first  radial  is  of  nearly  the  same  width  as  the 
second,  instead  of  being  much  wider ;  the  first  interradial  is  more  elongated,  and  the  two 
lower  sides  together  are  not  one  fourth  the  length  of  the  two  corresponding  sides  in  E. 
crassus.  The  second  interradials  are  also  more  elongate,  and  narrower.  The  base  shows 
a  tuberculately  pentagonal  form  not  possessed  by  the  Waldron  specimens. 

Eucalypiocrinus  ornatus  Hall.  Wis.  Geol.  Rep.  1861,  p.  20.  Differs  in  no  way  from  Hall's 
description,  except  that  the  first  interradial  plate  is  a  little  higher  than  wide  ;  and  our  casts 
do  not  exhibit  the  characters  of  the  exterior. 

One  of  our  specimens  possesses  a  sub-central  proboscis,  of  which  three  eighths  of  an  inch 
are  preserved,  exhibiting  such  a  taper  that  the  entire  length  would  seem  to  have  been  five 
or  six  eighths  of  an  inch.  Only  the  cast  of  the  proboscis  exists.  The  dome  is  depressed, 
and  the  base  of  the  proboscis  is  elevated  about  three  eighths  of  an  inch  above,  the  arm 
bases.  This  is  a  common  species,  and  may  be  at  once  distinguished  from  E.  chicac/oensis  by 
its  much  more  depressed  and  generally  sub-hemispherical  body.  This  is  probably  the  spe- 
cies mistaken  by  Worthen  for  E.  decorus,  which  it  resembles  in  form  while  it  is  amply  dis- 
tinct in  the  details  of  the  plates. 

Cart/ocrinus  ornatus  Say.  This  species  is  common,  and  many  of  the  specimens  exhibit, 
by  the  removal  of  the  exterior,  the  grooves  running  from  the  pores  to  the  margins  of  the 
plates,  as  shown  by  Hall,  Pal.  N.  Y.,  II.  pi.  xlix.  fig.  1,  u.  The  external  impression  of 
the  body  is  sometimes  extremely  well  preserved. 

Caryocystites  ct/Zindricus  Hall.  Geol.  Rep.  Wis.  1861,  p.  23  ;  figured  in  Rep.  for  1862, 
p.  69.  The  ovarian  aperture,  not  seen  in  the  typical  specimens,  is  very  distinct  in  a  fine 
specimen  belonging  to  the  Chicago  Academy  of  Sciences. 

STROPHOMENA  Raf. 
Strophomena  macra  W.  and  M. 

Plate  II.  figure  8. 

Shell  thin,  with  both  valves  nearly  plane  in  young  specimens ;  general  outline  semicir- 
cular, but  with  a  straight  hinge-line  projecting  somewhat  at  the  lateral  angles.  Ventral 
valve  very  slightly  elevated  in  the  umbonal  region,  deeply  concave  nearer  the  border  in 
old  individuals,  having  a  long,  moderately  wide  area  with  a  triangular  fissure ;  divaricator 


92  WINCHELL  AND   MARCY  ON   FOSSILS  FROM   THE 

scars  a  pair  of  small,  feeble,  diverging  pyriform  impressions,  separated  by  a  faintly  raised 
rostral  septum,  which  reaches  two  fifths  the  length  of  the  scars.  Inside  of  valve  showing 
numerous  faint,  irregularly  distributed  radiating  ridges  which  become  visible  about  mid- 
way between  the  beak  and  the  margin.  Sometimes  one  or  two  feeble  concentric  wrinkles 
a  little  beyond  the  middle  of  the  valve.  The  exterior  is  very  differently  marked.  It  pre- 
sents a  series  of  shallow,  flattish-concave,  radiating  furrows,  separated  by  abruptly  raised, 
narrow,  sharply  carinated  costae.  The  latter  double  in  number  near  the  middle  of  the 
valve  by  implantation  in  the  middle  of  the  intervening  furrows. 

Length  of  hinge-line  of  large  specimen,  1.8  inch ;  length  of  shell  from  beak  to  front 
margin,  1.21  inch;  transverse  diameter  of  fissure,  .39  inch;  greatest  width  of  area,  .15 
inch  ;  depth  of  ventral  valve,  .04  inch ;  length  of  divaricator  scars,  .5  inch. 

In  outline  and  surface  characters  of  the  casts  of  young  individuals,  this  species  resem- 
bles Leptcena  seiicea  Sow.,  but  the  divaricator  scars  are  very  much  smaller,  differently 
shaped,  and  more  feebly  impressed.  It  is  also  a  leaner  shell,  and  on  the  inside  shows  but 
faintly  the  costal  impressions  which  can  be  so  plainly  traced  around  the  margin  of  that 
species.  It  differs  similarly  from  Streptorhynchus  subplamis,  its  nearest  analogue  in  rocks  of 
the  same  age.  The  characters  of  the  exterior,  and  of  the  adult  shell  present,  on  the  con- 
trary, few  resemblances  to  the  species  with  which  we  have  compared  the  young. 

Strophomena  uiagareusis  W.  and  M. 
Plate  II.  figure  9. 

Shell  of  large  or  medium  size,  somewhat  hemispherical,  hinge-line  equal  to  the  greatest 
width,  producing  a  semicircular  outline.  Ventral  valve  extremely  ventricose,  regularly 
arched  from  beak  to  anterior  margin,  most  elevated  in  the  middle,  flattened  toward  the 
hinge  extremities  ;  beak  depressed,  incurved,  not  surpassing  the  hinge-line.  Area  moder- 
ately elevated  in  the  middle,  with  a  broad  triangular  foramen,  situated  nearly  in  the  plane 
of  the  commissure  of  the  two  valves,  delicately  striated  transversely.  Divaricator  scars  elon- 
gate-ovate, but  slightly  divergent,  reaching  one  third  the  length  of  the  valve;  occlusor 
scars  narrowly  linear,  closely  approximate;  rostral  septum  low,  one  third  the  length  of  the 
divaricator  scars.  Internal  surface  of  shell  finely  papillose  in  the  region  between  the  mus- 
cular scars  and  the  hinge-line ;  the  entire  inner  surface  marked  with  very  fine,  irregular, 
wavy  striae.  Ventral  valve  sometimes  with  a  shallow  undefined  sinus  each  side  of  a  low 
median  ridge. 

Length  of  hinge-line,  1.58  inch ;  length  of  shell,  1.34  inch ;  convexity  of  the  ventral 
valve>  .50  inch;  length  of  divaricator  scars,  .65  inch. 

We  have  endeavored  to  unite  this  species  with  some  of  those  already  recognized.  It 
belongs  to  the  group  embracing  S.  incequistriata,  liemisphcerica,  etc.  which  are  the  nearest  re- 
lated American  forms.  In  outline  it  resembles  the  first,  but  the  beak  is  less  projecting,  and 
the  striae  are  much  finer.  Unlike  8.  hemisphcerica  it  has  no  concentric  wrinkles  or  other 
markings ;  and  the  hinge-line  is  proportionally  longer,  the  muscular  scars  more  elongate 
and  narrower,  and  the  whole  structure  about  the  hinge  is  bolder  and  stronger.  Neither  does 
S.  hemisphcerica  exhibit  the  internal  granulations  so  conspicuous  in  our  species.  We  think, 
too,  that  our  species  is  always  even  more  ventricose  than  the  other.  Amongst  known  fos- 
sils of  the  same  age,  there  are  none  closely  related.  The  resemblance  of  S.  sttbplamts  and 
S.  semifasciata  is  quite  superficial,  and  no  more  can  be  said  of  S.  polenta,  of  the  Clinton 
group.  Amongst  foreign  species  it  approaches  nearest  to  S.  imbrex  Pander  and  Davidson. 


NIAGARA    LIMESTONE    OF    CHICAGO,    ILLINOIS.  93 

Strophomena  rkomboidalis'Wahl.  Numerous  excellent  examples  of  the  middle-silurian  type, 
showing  both  external  and  internal  characters.  We  shall  probably  discover  grounds  here- 
after for  a  division  of  this  nominal  species. 

STREPTORHYNCHUS   King. 

Streptorhynehus  hemiaster  W.  and  M. 

Plate  II.  figure  10. 

Shell  small,  semicircular,  hinge-line  the  longest  diameter;  in  some  specimens  slightly 
auriculate.  Ventral  valve  depressed-convex,  with  an  abruptly  elevated  beak,  truncated  by 
the  area  on  the  cardinal  side,  and  gently  twisted  toward  the  right ;  area  triangular,  nearly 
at  right  angles  with  the  plane  of  the  shell,  its  fissure  closed  by  a  convex  pseudo-deltidium 
of  one  piece.  Surface  marked  by  straight,  sharp,  radial  costse  which  double  in  number  by 
implantation  at  about  one  third  the  distance  from  the  beak  to  the  margin,  and  double 
again  nearer  the  margin.  Dorsal  valve  flat,  appearing,  in  the  condition  in  which  we  find 
the  specimens,  to  be  constituted  by  a  series  of  radiating,  rounded,  threadlike  ribs  which 
show  most  conspicuously  on  the  inside,  the  principal  ones  extending  from  the  beak  to  the 
margin,  and  increasing  in  number  by  implantation. 

Length  of  hinge-line  .38  inch ;  length  of  shell  .23  inch ;  height  of  area  of  ventral  valve 
.10  inch. 

Atrypa  reticularis  Dalm.  sp.  Abundant,  often  exhibiting  the  internal  structure  in  a 
beautiful  state  of  preservation. 

Atrypa  nodostriata  Hall.  Pal.  N.  Y.,  II.  272,  pi.  Ivi.  2.  Common,  in  an  imperfect  condition, 
but  in  some  instances  exhibiting  the  spiral  armature. 

Trematospira  Matihewsoni  McChesney.    New  Paleozoic  Fossils,  p.  71. 

Athyris  nitida  Hall  sp.  Pal.  N.  Y.,  II.  268,  pi.  Iv.  1,  2.  Occurs  in  the  typical  form,  and 
the  variety  oblata  Hall. 

Nucleospira  sp  ?  A  small  pyriformly  ventricose  species,  exhibiting  the  internal  struct- 
ure, but  too  imperfect  for  description.  We  suspect  this  is  the  species  referred  to  by  Hall 
(Iowa  Rep.  p.  73,  note),  as  a  Spirigera,  occuring  at  Leclaire,  Iowa,  in  great  numbers. 

SPIRIFERA  Sow.    Martinia  McCoy. 
Spirifera  (Martiaia)  similior  W.  and  M. 

Outline  subcircular,  transverse  diameter  greatest,  gently  rounded  from  the  sides  to  the 
cardinal  margin  ;  hinge-line  about  two  thirds  the  greatest  width  of  the  shell.  Ventral 
valve  ventricose,  gently  convex  to  the  very  margin  on  all  sides,  deepest  at  about  one  third 
the  distance  from  the  beak  to  the  anterior  margin ;  beak  incurved  and  slightly  surpassing 
the  hinge-line,  overhanging  a  large  triangular  fissure,  without  noticeable  area.  A  trace  of 
a  mesial  septum  extends  from  the  beak  one  third  the  length  of  the  valve.  In  some  speci- 
mens no  sinus  whatever  can.be  discerned  ;  in  others,  a  shallow  and  obsolete  one  ;  in  others 
still,  one  or  two  inconspicuous  undulations  each  side  of  a  mesial  sinus.  Surface  of  cast 
otherwise  smooth,  or  with  numerous  fine  concentric  wrinkles.  In  one  specimen  faint  radi- 
ating lines  may  be  doubtfully  detected. 


94  WINCHELL   AND   MARCY   ON   FOSSILS  FROM   THE 

Length  of  shell,  .57  inch;  transverse  diameter,  .80;  height  of  umbo  of  ventral  valve,  .31 
inch. 

In  its  smooth  exterior,  and  gently  undulate  margin,  this  species  calls  to  mind  Spirifer  U- 
costatits  Hall  ;•  and  we  were  at  first  inclined  to  regard  it  as  a  variety  of  that  species;  but  the 
beak  is  always  less  prominent  and  less  incurved,  and  the  sinuations  of  the  exterior  are 
much  less  apparent,  and  in  some  specimens  entirely  wanting. 

It  is  an  abundant  species  at  Chicago ;  and  in  some  instances  one  of  the  spires  has  been 
found  in  a  complete  state  of  preservation,  showing  that  it  consists  of  seven  turns  conically 
arranged. 

Spirifera  radiata  Sowerby.  Silur.  Sys.  637,  pi.  xii.  fig.  6,  and  638,  pi.  xxi.  fig.  5.  Very 
good  ventral  valves  of  this  species  occur,  and  in  one  instance,  a  fine  specimen  with  the 
valves  united.  Another  specimen  exhibits  the  internal  structure,  showing  that  the  spire  is  a 
delicate  hollow  tube  of  about  14  turns,  of  which  11  are  preserved.  In  these  specimens  it  is 
interesting  to  observe  that  the  margin  is  distinctly  plicated,  as  in  the  Dudley  specimens  from 
England.  According  to  Hall,  (Pal.  N.  Y.,  II.  265,)  this  character  is  not  observed  in  the  New 
York  specimens  of  the  species.  Neither  does  it  occur  in  specimens  in  our  possession 
from  Waldron,  Indiana. 

Spirifera  crispa  Sowe.rby.  Silur.  Sys.  624,  pi.  xii.  fig.  8.  Each  spire  has  about  ten  turns, 
the  first  of  which  corresponds  to  the  sinus  bounding  the  mesial  elevation.  The  crus  ex- 
pands into  a  little  plate  and  becomes  coincident  with  the  dental  lamella  of  the  opposite 
valve.  A  little  curved,  barb-like  branch  departs  from  each  of  the  crura,  on  the  ventral 
side,  and  the  two  perhaps  meet  together  in  the  manner  of  Zygospira  Hall,  though  in  a 
different  position. 

PENTAMERUS    Sowerby. 

Fentamerus  chicagoensis  W.  and  M. 

Plate  H.  figure  11. 

Shell  of  moderate  size,  the  commissure,  (including  the  hinge-line)  presenting  a  somewhat 
semicircular  outline ;  but  in  consequence  of  the  prominence  of  the  beak  of  the  ventral 
valve,  the  outline  presented  by  a  view  from  this  side  is  obtusely  sectoral.  The  ventral 
valve  is  very  ventricose,  with  the  beak  recurved  over  that  of  the  dorsal  valve.  The  highest 
point  of  the  convexity  is  two  fifths  the  distance  from  the  beak  to  the  front  margin.  A  nar- 
row, rather  deep  and  distinct  sinus  extends  from  the  umbo  to  the  anterior  margin,  which  is 
bounded  on  each  side  by  a  stout  obtuse  rib  considerably  elevated  above  the  general  contour. 
In  other  words,  this  valve  may  be  said  to  present  a  median  ridge  which  is  deeply  divided 
in  the  middle.  Following  each  of  the  median  ribs  are  three  others,  smaller  than  the  two 
middle  ones,  and  of  which  the  first  is  less  developed  than  the  other  two.  The  last  two  ribs 
only  reach  half  way  to  the  beak.  Still  nearer  the  right  and  left  extremities  the  surface 
seems  to  be  plane,  but  near  the  beak  are  five  or  six  radial  striae  on  each  side.  No  other  sur- 
face markings  are  visible  either  on  the  shell  or  the  cast. 

Length  from  beak  to  anterior  margin,  .65  inch;  greatest  transverse  diameter  —  lying 
midway  between  the  anterior  and  cardinal  margins  —  .65  inch. 

The  form  of  this  species  is  similar  to  that  of  P.  galeatus  Dalman,  but  the  extremities  are 
less  rounded,  and  the  costae  are  fewer  and  less  regular.  It  is  related  to  P.  trisinuatus  Me- 


NIAGARA   LIMESTONE   OF    CHICAGO,   ILLINOIS.  95 

Chesney,  but  our  species  has  two  additional  ribs  on  each  side  of  the  ventral  sinus.  We 
have  not  access  to  Hall's  description  of  P.  ?  ventricosus  from  the  Niagara  limestone  of  Wis- 
consin. 

Rhynchonella  negleda  Hall.     Pal.  N.  Y.,  II.  274,  pi.  Ivii.  fig.  1,  a -p. 

PTERINEA  (Goldf.)  Meek. 
Pterinea  volans  W.  and  M. 

Shell  large,  very  oblique,  with  an  extended  hinge-line,  and  alate  posterior  extremity. 
General  outline  nearly  semicircular.  Left  valve  moderately  inflated  anteriorly,  flattened  in 
the  posterior  half;  beak  small,  nearly  terminal,  incurved,  not  surpassing  the  hinge-line; 
whole  pallial  outline  regularly  circular,  except  a  rather  deep  sinus  beneath  the  posterior 
hinge  extremity.  Cartilage  facet  not  certainly  determined  ;  in  one  small  specimen  it  ap- 
pears to  be  very  wide,  with  four  or  five  furrows.  External  surface  marked  by  strong  ribs 
which  bifurcate  and  become  wavy  beyond  the  middle  in  old  shells ;  the  ribs  becoming 
abruptly  much  smaller  on  the  posterior  wing.  Besides  the  ribs,  the  superficial  layer  of  the 
shell  is  cancellated  by  strong  concentric  and  feeble  radiating  ridges.  The  costae  show  dis- 
tinctly on  the  cast,  except  on  the  posterior  wing. 

Length  of  hinge-line,  2.1  inches ;  greatest  height  of  shell  (at  middle  of  hinge-line,)  1.5 
inch;  convexity  of  left  valve,  .26  inch. 

This  species  differs  from  P.  stricecosta,  in  its  less  rugose  reticulations,  stronger  ribs,  and 
straight,  instead  of  curved,  umbonal  slope.  Young  specimens  resemble  P.  (Avicula)  emaceraia 
Hall,  but  the  posterior  wing  is  more  expanded,  so  as  to  constitute  half  the  surface  of 
the  valve. 

Pterinea  revoluta  W.  and  M. 

Plate  II.  figure  12. 

A  distinct  and  well-marked  species  known  only  by  the  impression  of  the  left  valve,  which 
is  beautifully  restored  by  means  of  a  gutia  percha  cast.  This  is  rotund-quadrate  in  outline, 
ventricose,  with  depressed  beak,  hinge-line  but  slightly  produced  posteriorly.  Anterior 
margin  regularly  rounded  to  the  ventral  side ;  posterior  slightly  sinuate  below  the  hinge 
extremity ;  greatest  dimension  from  the  hinge  to  the  circularly  curved  ventral  side.  The 
surface  is  marked  by  seven  or  eight  concentric,  lamellose  folds  or  layers  of  substance,  each 
of  which  is  ornamented  by  a  distinct  set  of  numerous  rounded  striae.  These  are  not  con- 
tinuous from  fold  to  fold  ;  neither  are  they  straight,  nor  strictly  radiating  from  the  beak ; 
but  they  generally  exhibit,  especially  toward  their  upper  ends,  a  convexity  toward  the  pos- 
terior side ;  in  other  words,  the  upper  ends  of  the  striae  on  each  concentric  fold  are  bent 
forward.  The  margin  of  the  valve  is  strongly  revolute. 

Length  from  beak  to  ventral  side,  .56  inch ;  length  along  hinge-line,  about  .47  inch. 

This  curious  and  pretty  species  recalls  P.  planulata  Conrad,  and  P.  hiaiis  McCoy,  from  the 
Amesbury  limestone,  but  the  description  given  above  distinguishes  it  decisively  from  these 
and  all  others  known  to  us. 

Pterinea  cyrtodontoides  W.  and  M. 

Shell  of  moderate  size,  oblique ;  hinge-line  equal  to  greatest  width ;  its  extremities 
rounded,  scarcely  alate ;  beaks  anterior  to  the  middle.  Left  valve  ventricose,  with  an  in- 


96  WINCIIELL   AND   MARCY   ON    FOSSILS    FROM   THE 

curved  beak,  an  umbonal  slope  forming  an  angle  of  about  65°  with  the  hinge-line,  most  ele- 
vated about  midway  between  the  dorsal  and  ventral  margins ;  anterior  margin  parallel  with 
umbonal  slope,  slightly  sinuated  below  the  hinge  extremity  ;  ventral  and  posterior  margins 
circularly  rounded.  Cartilage  facet  narrow,  with  apparently  a  single  posterior  linear 
groove,  deepest  near  the  hinge  extremity,  and  another  short,  similar  groove  anterior  to  the 
beak.  Surface  of  cast  with  feeble  concentric  striae 

Length  of  hinge-line,  .66  inch  ;  greatest  length  of  shell,  .70  inch;  height,  .78  inch;  depth 
of  left  valve,  22  inch;  length  of  anterior  end,  .25  inch;  of  posterior  end  .41  inch;  projection 
of  beak,  .08  inch. 

Differs  from  Avicula  undata  Hall,  by  its  shorter  hinge-line,  more  projecting  beak,  and 
greater  ventricosity. 

Ptcrinea  stricecosta  McChesney,  sp.  Ambonychia  stricecosta  McChesney.  "New  Paleozoic 
Fossils,"  p.  88.  This  fine  species,  to  the  general  form  of  Pterinea,  adds  a  cartilage  facet 
with  at  least  four  longitudinal  furrows.  In  one  of  our  specimens  the  facet  is  .18  inch  wide. 

Pterinea  negkcta  McChesney.  sp.  "New  Paleozoic  Fossils,"  p.  88.  Very  abundant  in  casts, 
often  with  the  two  valves  united.  Exterior  seldom  seen.  This  species  possessed  a  very 
wide  cartilage  facet  which  is  rarely  seen. 

CLIDOPHORUS  Conrad. 

Clidophorus  m'chesneyanus  W.  and  M. 

Plate  III.  figure  3. 

Shell  equivalve,  with  the  general  aspect  of  an  Orthonota  ;  but  very  slightly  widening  pos- 
teriorly ;  posterior  end  symmetrically  truncate-rounded  above  and  below,  so  that  the  most 
projecting  extremity  is  on  the  line  midway  between  the  dorsal  and  ventral  sides.  The  dor- 
sal side  is  erect,  compressed,  and  the  hinge-line  is  three  fourths  as  long  as  the  shell.  The 
anterior  margin  is  rounded.  The  beak  is  very  near  the  anterior  end  and  projects  slightly 
above  the  hinge.  Shell  rather  ventricose — the  umbonal  ridge  lying  above  the  middle  and 
vanishing  in  the  direction  of  the  posterior  extremity.  The  casts  prove  the  existence  of 
deep  pyriform  pits  for  the  anterior  adductors,  which  are  bounded  posteriorly  by  an  ele- 
vated margin  scarcely  possessing  the  characters  of  the  "clavicular  ridge"  of  Clidophorus. 
The  posterior  scars  cannot  be  detected  in  any  of  the  specimens.  In  the  left  valve  was  a 
deep  cardinal  pit,  with  a  stout  cardinal  tooth  in  front  of  it.  The  surface  of  casts  is  marked 
by  two  or  three  deep  furrows  of  growth,  with  several  smaller  incremental  lines.  Restored 
exteriors  present  the  same  character  with  increased  sharpness. 

Length,  1.11  inch;  greatest  width — three  fifths  the  distance  from  anterior  to  posterior 
extremity —  .59  inch  ;  length  of  anterior  end,  .15  inch ;  thickness  of  both  valves,  .4  inch. 

This  species  differs  from  Orthonota  and  Modiohpsis  as  defined  by  McCoy,  in  the  possession 
of  cardinal  teeth,  and  from  the  first,  in  its  deep  anterior  muscular  impression.  It  differs 
from  Orthonota  as  restricted  by  Pictet,  in  the  absence  of  numerous  arcaciform  teeth.  At 
the  same  time  it  has  not  the  form  of  Modiolopsis,  nor  its  byssiferous  sinus  and  oblique 
depression;  and  we  are  unacquainted  with  any  established  genus  with  which  it  strictly 
agrees. 

We  have  dedicated  the  species  to  Prof.  J.  H.  McChesney,  U.  S.  Consul  at  Newcastle-on- 
Tyne,  for  his  investigations  made  at  the  typical  locality. 


NIAGARA    LIMESTONE    OF    CHICAGO,   ILLINOIS.      ,  07 

EDMONDIA  de  Koninck. 

Edmondia  Nilesi  W.  and  M. 
Plate  II.  figure  13. 

Shell  rather  small,  equivalve,  transverse,  once  and  a  half  as  long  as  wide,  subventricose 
with  a  prominent  umbonal  ridge  extending  to  the  postero-ventral  angle,  becoming  some- 
what acute  near  the  beak,  and  leaning  over  toward  the  hinge,  so  as  to  cause  the  subter- 
minal  beaks  to  project  considerably  beyond  the  slightly  arched  hinge-line  and  to  have  their 
apices  twisted  forward.  The  general  outline  is  oval,  a  little  widening  posteriorly,  and  flat- 
tened along  the  dorsal  side  as  far  as  the  middle.  Beneath  the  beaks  is  an  anterior  lunette, 
forming  a  small  notch  in  the  outline.  Ventral  side  gently  curved.  Shell  thin ;  its  exterior 
nearly  smooth,  and  marked  by  faint  incremental  lines.  The  casts  do  not  enable  us  to  deter- 
mine the  character  of  the  muscular  impressions.  Greatest  width,  a  little  posterior  to  the 
middle;  greatest  thickness,  a  little  anterior  to  it.  In  the  casts  the  beak  is  less  terminal 
than  in  the  shell. 

Length,  .95  inch;  greatest  width,  .60  inch;  greatest  thickness  of  both  valves,  .40  inch. 

We  have  some  hesitancy  in  making  a  generic  reference  of  this  species,  thinking  it  may 
be  an  Orthonota  ;  but  the  apparently  edentulous  hinge,  and  the  slightly  convex  dorsal  and 
ventral  sides  seem  to  point  to  Edmondia. 

Dedicated  to  W.  H.  Niles  of  Cambridge,  Mass.,  the  discoverer  of  the  species. 

Amboni/ckia  mytiloidea  Hall.  Wis.  Geol.  Rep.  1860,  p.  2.  Casts  show  concentric  folds  near 
the  margin.  The  shell  was  apparently  thick.  Resembles  Myalina  mytiliformis  Hall,  (Pal. 
N.  Y.,  100,  PL  xxx.  fig.  1,)  from  the  Gray  sandstone  of  the  Clinton  group. 

CONOCARDIUM  Bronn. 
Conocardium  niagarense  W.  and  M. 
Plate  II.  figure  14. 

Shell  small,  ventricose,  about  twice  as  long  as  wide,  with  central  beaks  and  finely  costate 
exterior.  The  truncation,  or  boundary  of  the  ribbed  portion  is  posterior  to  the  middle  of  the 
shell,  and  forms,  on  the  posterior  side,  an  angle  of  58°  with  the  straight,  elongate  dorsal 
side.  The  form  of  this  end  resembles  the  outside  of  a  salver.  The  rostrum  is  produced 
into  a  linear  extension  reaching  as  far  behind  the  beak  as  the  opposite  extremity  is  in  front 
of  it.  The  beak  is  incurved,  but  not  perceptibly  turned  one  way  or  the  other.  The  body  of 
the  shell  is  ornamented  by  eighteen  sharp  and  delicate  ribs,  the  anterior  one  forming  an 
angle  of  28°  with  the  hinge-line,  and  the  included  space  being  apparently  smooth. 

Length  of  shell,  about  .46  inch;  height,  .26  inch. 

This  shell  is  sometimes  found  with  the  two  valves  united.  It  is  the  only  species  of  Cono- 
cardium known  to  us  in  the  Niagara  group. 

It  will  be  perceived  that  we  denominate  the  rostral  extremity  the  posterior  one,  contrary 
to  the  usage  of  Pictet,  McCoy,  and  others,  but,  as  we  believe,  more  in  accordance  with  anal- 
ogies. 

5 


98  WINCIIELL   AND   MARCY  ON   FOSSILS    FROM   THE 

PLEUROTOMARIA  Defrance. 

Pleurotomaria  gonopleura  W.  and  M. 

Plate  III.  figure  4. 

Shell  conical,  somewhat  flattened  on  the  upper  portion  of  the  whorls  and  on  the  base. 
Number  of  whorls  six  or  seven,  enlarging  with  regularity ;  suture  moderately  impressed  ; 
keel  near  the  lower  side  of  the  whorl,  quite  prominent;  whorl  rounded  below  this,  to  the 
suture ;  above  the  keel,  nearly  half  way  to  the  suture  is  another  low  ridge  separated  from 
the  first  by  a  concave  belt ;  above  this  ridge  the  whorls  are  flattened  convex.  Surface 
marked  only  by  incremental  lines  which  incline  backwards  in  passing  from  the  suture  to  the 
keel,  and  continue  in  the  same  direction  into  the  umbilicus,  suffering  a  slight  retral  inflec- 
tion in  passing  the  peripheral  band. 

Height,  1.19  inch  ;  diameter  of  base,  .98  inch ;  height  of  last  whorl,  .50  inch. 

This  species,  though  resembling  P.  Hoyi  Hall,  from  the  Racine  limestone,  has  two  or  three 
more  volutions ;  and  has  the  band  on  the  lower,  instead  of  the  upper,  angle  of  the  whorls. 

Pleurotomaria  Halei  Hall?  Wis.  Rep.  1861,  p.  34.  Abundant  specimens  of  a  Pleurotoma- 
ria occur,  which  agree  generally  with  the  above  species.  They  differ  as  follows  : — Height 
equal  to  transverse  diameter,  instead  of  two  thirds  that  diameter;  number  of  volutions 
five  or  six  instead  of  three  or  four;  number  of  revolving  ridges  on  the  upper  side  of  the 
volution  five  or  six,  instead  of  ten  or  twelve.  The  periphery,  moreover,  can  hardly  be  said 
to  be  sub-angulated. 

To  Hall's  description  it  may  be  added,  that  the  under  side  of  the  body  whorl  is  marked 
by  about  thirteen  wavy,  revolving  ridges,  alternately  larger  and  smaller,  intersected  by 
transverse  striae  emerging  from  the  umbilicus.  It  resembles  P.  decussata  Sandberger,  from 
the  stringocephalenkalk  of  Nassau. 

We  are  in  possession  of  the  casts  of  the  umbilical  cavity  of  a  very  large  Pleurotomaria 
which  may  belong  to  this  species.  The  revolving  ridges  rise  obliquely  from  the  umbilical 
cavity,  and  are  intercepted  nearly  at  right  angles  by  a  set  of  less  numerous  ridges,  also  ris- 
ing from  the  umbilicus,  and  curving  in  the  opposite  direction.  Some  of  these  casts  show 
that  the  umbilical  cavity  exposed  five  whorls.  The  diameter  of  the  base  of  the  largest 
individual  must  have  been  two  and  a  half  inches.  This  individual  was  reversed,  or  sinis- 
tral.  It  is  not  unlikely  that  the  great  size  of  the  umbilicus  in  these  casts,  and  the  inter- 
rupted character  of  the  ridges  emerging  from  it,  and  perhaps  also  the  great  size  of  the  speci- 
mens, give  indications  of  an  undescribed  species. 

Pleurotomaria  Hoyi  Hall.  Wis.  Geol.  Rep.  1861,  p.  35.  No  flattening  appears  on  the  lower 
side  of  any  of  the  volutions  of  our  specimens. 

Pleurotomaria  sigaretoides  W.  and  M. 
Plate  III.  figure  5. 

Shell  small,  depressed-conical,  oblique,  sinistral  (in  our  single  specimen),  consisting  of  three 
or  four  rapidly  enlarging  whorls.  The  whorls  are  flattened  on  the  exterior,  leaving  a  linear 
suture.  The  last  whorl  is  two  and  a  half  times  as  broad  on  the  flattened  exterior  as  the 
penultimate  whorl,  sharply  angulated  at  the  periphery,  which  forms  the  outer  boundary  of 
the  flat,  or  shallow  funnel-shaped  base.  It  is  supposed  that  this  angle  is  the  place  of  the 


NIAGAEA    LIMESTONE    OF    CHICAGO,    ILLINOIS.  99 

band,  since  the  surface  of  the  body  whorl  shows  numerous  transverse  lines,  curving  re- 
trally  from  the  suture  to  this  peripheral  angle.  The  rapid  increase  of  the  whorls  throws  the 
apex  much  nearer  to  one  side  than  the  other. 

Height,  30  inch;  height  of  body  whorl,  .18  inch;  diameter  of  base,  .44  inch;  apical 
angle,  76°. 

PLATYCERAS   (Conrad)  Hall. 

Platyceras  campanulatum  W.  and  M. 
Plate  II.  figure  16. 

Whorls  three  or  four,  in  contact ;  spire  scarcely  elevated  above  the  last  volution ;  last 
volution  greatly  enlarged,  with  a  nearly  circular  section,  an  angulated  periphery  and 
trumpet-shaped,  circular  aperture.  Columella  none  ;  umbilicus  minute ;  lip  not  modified 
by  the  penultimate  whorl.  Peripheral  ridge  in  the  middle  of  the  whorl  or  a  little  above. 
Surface  marked  by  extremely  faint  longitudinal  striae,  and  by  remote,  obscure,  transverse 
ridges,  not  retroflected  in  passing  the  periphery. 

This  species  seems  to  be  the  representative  of  Platyostoma  niagarense  Hall.  It  is  inferior 
in  size  to  full-grown  specimens  of  that  species,  and  differs  from  it  in  the  possession  of  an 
umbilicus,  and  in  the  completeness  of  its  peristome.  It  is  to  be  observed,  however,  that 
the  entire  peristome  is  possessed  by  many  specimens  from  Waldron,  Indiana,  that  have 
been  referred  to  Platyostoma  niagarense  ;  and  that  the  two  genera  run  inseparably  together. 
Should  we  retain  but  one  of  these  generic  names,  Platyceras  has  the  prior  claim. 

HOLOPEA   Hall. 

Holopea  niagarensis  W.  andM. 

Plate  II.  figure  18. 

Shell  small,  consisting  of  four  or  five  very  convex  whorls  in  a  moderately  elevated  spire 
having  an  apical  angle  of  58° ;  the  last  whorl  more  rapidly  enlarged  than  the  preceding, 
rounded  below,  and  apparently  excavated  into  an  umbilicus.  Suture  deeply  impressed, 
each  whorl  being  almost  completely  above  the  level  of  the  preceding  one.  No  surface- 
markings  visible  on  casts. 

Height,  .25.  inch ;  diameter  of  last  whorl,  .20  inch. 

Holopea  chicagoensis  W.  and  M. 
Plate  II.  figure  18. 

Shell  small,  consisting  of  five  or  six  moderately  convex  whorls  in  a  sub-elevated  spire, 
having  an  apical  angle  of  about  42° ;  body  whorl  proportionally  higher,  but  not  more  en- 
larged than  the  preceding.  The  outer  side  of  the  whorls  is  somewhat  flattened,  becoming 
rapidly  incurved  in  the  upper  part,  toward  the  suture ;  whorls  apparently  overlapping. 
Base  of  last  whorl  rounded  into  a  minute  umbilicus;  transverse  section  of  whorl  nearly 
circular.  Surface  of  casts  smooth. 

Height,  .35  inch;  diameter  of  last  whorl,  .25  inch. 

These  two  species  of  Holopea  —  existing  only  in  the  form  of  casts  —  it  is  impossible  to 
distinguish  certainly  from  Cycloncma,  though  that  genus  is  said  to  be  always  exumbilicate. 


100  WINCHELL    AND    MARCY   ON   FOSSILS    FROM    THE 

They  are,  however,  quite  distinct  specifically  from  anything  at  present  known  to  us  in  the 
upper  silurian. 

Loxonema  sululata  Conrad  (Murchismria  sululata  Hall).  No  decisive  characters  separate  our 
forms  from  the  above  species  of  the  Clinton  group.  The  number  of  volutions  is  nine  or 
ten.  Indications  of  sigmoid  incremental  lines,  without  the  faintest  trace  of  a  peripheral 
band  or  apertural  slit,  induce  us  to  refer  our  specimens  to  Loxonema,  as  was  originally  done 
by  Conrad  with  the  New  York  specimens.  It  differs  from  its  foreign  analogue,  Loxonema, 
sinuosa  Sowerby,  by  feebler  transverse  striae  and  a  deeper  suture,  distinguishing  it  from 
Holopella.  This  species  is  quoted  from  the  Niagara  group  of  Canada  West.  Geol.  of  Canada, 
p.  326. 

SUBULITES   Conrad. 

Subulites  brevis  W.  and  M. 

Plate  II.  figure  19. 

A  species  apparently  referable  to  this  genus  is  evidently  distinct  from  any  known  form 
belonging  to  this  age.  Aperture  unknown ;  number  of  whorls  at  least  five  or  six,  rather 
rapidly  tapering,  flattened  on  the  exterior,  widely  overlapping,  attenuated  to  a  sharp  edge 
on  the  upper  side,  producing  a  shallow  linear  suture  which  is  also  very  oblique.  Transverse 
section  of  whorl  narrowly  crescentic.  No  surface  characters  imprinted  upon  the  casts. 
This  species,  in  robustness  and  number  of  whorls,  is  intermediate  between  S.  elongatus  and 
S.  ventricosus.  The  apical  portion  in  all  of  our  numerous  specimens  is  distinctly  bent  to 
one  side. 

BELLEKOPHON  Montfort.   BUCANIA  Hall. 

Bellerophon  (Bucania)  perforatus  W.  and  M. 

Plate  III.  figure  7. 

Shell  large,  sub-discoid,  with  about  four  whorls  moderately  impressed,  and  an  umbilical 
cavity  exposing  all  the  volutions.  Aperture  suddenly  and  broadly  expanded,  with  the  lip 
almost  reflexed.  Transverse  section  of  whorl  circular,  with  an  indentation  on  the  ventral 
side.  Dorsum  of  last  whorl  with  a  low  carina  on  which  are  elevated  a  series  of  elongated 
nodes  becoming  somewhat  continuous  near  the  aperture  —  the  length  of  the  nodes  gener- 
ally about  equal  to  the  distance  between  them.  These  are  visible  on  the  cast,  which  also 
imperfectly  preserves  some  longitudinal  markings.  The  latter,  near  the  aperture,  are  raised 
bands  with  intervening  spaces  of  equal  width,  and  some  indications  of  a  general  longitudi- 
nally striated  surface.  No  nodes  exist  on  the  young  shell.  Exterior  of  shell  marked  by 
numerous  sharp,  abruptly  raised  longitudinal  ridges,  which  increase  rapidly  by  implant- 
ation in  the  vicinity  of  the  trumpet-shaped  aperture.  The  nodes  of  the  shell  appear,  near 
the  aperture,  to  have  been  completely  perforated,  —  a  circumstance  which  seems  to  be 
only  an  exaggerated  condition  of  the  nodes,  as  the  latter  are  but  apertural  modifications 
of  the  continuous  carina. 

Transverse  diameter  of  aperture  at  least  2.56  inches ;  transverse  diameter  of  whorl,  one 
third  of  an  inch  back  from  the  margin  of  the  aperture,  1.58  inch.  —  one  inch  back,  1.42 
inch. 

This  may  be  the  Bucaiw  pervoluta,  McChesney,  though  that  is  described  as  below  medium 


NIAGARA   LIMESTONE   OF    CHICAGO,    ILLINOIS.  101 

size  ;  and  no  mention  is  made  of  the  very  conspicuous  dorsal  nodes.  McChesney  has  also 
described  B.  chicagoensis  from  the  same  quarries,  but  he  expressly  states  that  the  cast  is 
destitute  of  a  carina.  Our  species  may  also  be  compared  with  B.  (Bucania)  angustata 
Hall,  as  figured  in  the  Geology  of  Canada,  p.  344.  There  is  no  comparison,  however,  be- 
tween the  apertures  or  dorsal  characters  of  the  two. 

Orthoceras  Scammoni  McChesney.  New  Paleozoic  Fossils,  p.  92.  Specimens  unusually 
well  preserved.  We  may  add  to  the  characters  given  by  McChesney,  the  following :  The 
siphon  is  .52  inch  in  diameter,  at  a  place  where  the  shell  has  a  diameter  of  1.77  inch.  In 
the  same  specimen,  at  the  distance  of  four  inches,  the  siphon  is  .5  inch  in  diameter,  and  the 
shell  has  become  1.38  inch.  The  siphon  tapers  less  rapidly  than  the  shell,  and  is  about  one 
third  the  diameter  of  the  shell.  In  the  same  specimen  the  diameter  of  the  larger  end  is 
2.2  inches,  being  the  largest  specimen  seen.  Nine  and  a  half  inches  from  here  the  diameter 
has  diminished  to  one  inch.  The  distances  of  four  successive  septa,  where  the  mean  diam- 
eter of  the  shell  is  1.4  inch,  are  .34,  .45,  .41,  .40  —  the  mean  being  .40.  Strife  of  growth 
two  and  a  half  to  three  in  the  space  of  one  tenth  of  an  inch. 

This  species  closely  represents  0.  cancellatum  Hall,  but  we  have  not  been  able  to  detect 
any  longitudinal  striae  between  the  ridges. 

Orthoceras  nodocostum  McChesney.  New  Pal.  Fossils,  p.  94.  Our  specimens  enable  us  to 
complete  McChesney's  description. 

Shell  very  gradually  tapering  ;  annulated  by  a  raised  rounded  ring  corresponding  to  each 
chamber,  and  situated  a  little  in  front  of  the  middle  of  the  chamber.  Intervals  between 
the  rings  regularly  concave.  Septa  rather  deeply  concave,  crossing  the  shell  with  a  de- 
viation of  three  or  four  degrees  from  a  right  angle ;  their  distance  asunder  being  one 
third  the  diameter  of  the  shell.  No  annular  strias  can  be  seen  in  our  specimens.  The 
longitudinal  ridges  are  barely  discernible  on  the  shell,  and  leave  no  trace  upon  the  cast. 
The  siphon  is  cylindrical,  and  about  one  fourth  the  diameter  of  the  shell. 

The  distances  apart  of  four  successive  septa,  in  a  region  where  the  mean  diameter  is  .65 
inch,  are  .20,  .22,  .22,  .21,  giving  a  mean  distance  of  .21  inch. 

The  absence  of  concentric  striae,  and  the  presence  of  faint  longitudinal  ridges,  distinguish 
this  species  from  0.  undulatum  Hisinger. 

Orthoceras  Laphami  McChesney,  New  Pal.  Foss.  p.  91. 

GOMPHOCERAS  Sowerby. 

Gomphoceras  Marcyse  W.  and  M. 

Plate  III.  figure  8. 

Shell  of  moderate  size,  perfectly  straight.  The  outer  chamber,  in  connection  with  the 
penultimate  chamber,  gives  an  outline  which  is  neatly  and  symmetrically  elliptic,  with  a  little 
flattening  at  each  end.  That  portion  of  the  shell  between  the  penultimate  chamber 
and  the  apex  is  gradually  tapering.  Transverse  section  elliptic,  with  transverse  axis  to 
dorso-ventral  as  27  to  29  or  30.  Apertural  extremity  constricted  in  a  regularly  increasing 
ratio  to  the  ventral  lobe  of  the  aperture,  beyond  which  the  constriction  proceeds  on  the 
sides,  in  the  same  manner  as  far  as  the  lateral  lobes  of  the  aperture.  The  aperture  is  trisin- 
uate ;  the  two  lateral  sinuses  are  situated  a  little  back  of  the  central  axis,  and  are  separated 
from  each  other  by  a  transverse  oral  axis,  equal  to  one  half  the  greatest  transverse  diam- 

6 


102  WINCHELL    AND   MAECY   ON   FOSSILS   FROM   THE 

eter  of  the  shell.  The  ventral  sinus  projects  nearly  as  far  as  the  most  prominent  portion 
of  the  shell  on  the  ventral  side ;  and  is  bounded  laterally  by  the  two  projecting  lips  of  the 
aperture.  The  siphon  is  of  medium  size,  strongly  moniliform,  situated  on  the  greater  axis,  one 
eighth  that  axis  or  less,  from  the  ventral  side.  The  septa  are  deep,  regularly  concave ;  the 
penultimate  chamber  is  one  sixth  the  depth  of  the  chamber  of  habitation.  Surface  of  casts 
marked  by  numerous  incremental  ridges,  which  are  deeply  sinuate  on  the  ventral  side. 

Length  of  last  two  chambers,  1.6  inch ;  greatest  transverse  diameter,  1.09 ;  greatest 
dorso-ventral  diameter,  1.16 ;  depth  of  penultimate  chamber,  .20 ;  dorso-ventral  axis  of 
the  aperture,  .84 ;  transverse  axis,  .60 ;  diameter  of  siphon,  .09  ;  distance  from  ventral  side, 
.16.;  concavity  of  penultimate  chamber,  .18. 

This  unique  and  elegant,  and  rather  abundant  species  is  amply  distinct  from  anything 
known  to  us.  There  is  indeed  no  other  with  which  it  can  be  compared,  though  it  approaches 
nearest  to  Gomphoceras  pyriforme  Sowerby. 

LITUITES  Breynius. 
Lituites   Hercules  W.  and  M. 
Plate  III.  figure  9. 

Shell  very  large,  apparently  forming  less  than  a  complete  whorl  in  any  of  the  specimens 
seen.  Dorsum  and  sides  flattened-convex  —  the  latter  less  flattened  than  the  dorsum. 
Septa  moderately  concave,  plane,  much  flatter  in  the  middle  than  around  the  margins ;  si- 
phon rather  small,  central.  Greatest  transverse  diameter  three  fourths  the  distance  from 
the  dorsal  to  the  ventral  side,  causing  the  lateral  surfaces  to  approximate  dorsally. 

Surface  ornamented  only  by  encircling  striae  which  at  intervals  aggregate  into  irregular 
undulations.  The  striae  curve  backwards  on  the  sides  and  make  a  further  deep  retral  sinus 
across  the  dorsum. 

Dorso-ventral  diameter,  4.25  inches;  transverse  diameter,  4.12;  diameter  of  siphon,  .22; 
depth  of  dorsal  sinus  of  the  striae,  about  one  inch.  The  diameter  of  the  shell  from  the 
mouth  to  the  opposite  side  was  from  seven  to  nine  inches. 

One  of  our  specimens  is  an  impression  of  the  shell  in  the  rock.  This  shows  that  the 
apex  of  the  whorl  presented  an  obtuse  termination  more  than  an  inch  in  diameter. 

Cyrtoceras  Fosteri  Hall,  (Wis.  Eep.  1861,  p.  41).  The  specimens  in  our  collection  enable  us 
to  add  to  Prof.  Hall's  description  the  following  characters :  Shell  rather  more  rapidly  ex- 
panding toward  the  aperture,  which  is  sinuate  on  the  dorsal  side.  The  exterior  is  marked 
by  incremental  lines,  which,  on  the  dorsum,  are  correspondingly  sinuate.  The  two  diame- 
ters of  the  aperture  in  one  of  our  specimens  are  1.22  and  1.5  inch ;  depth  of  the  last  cham- 
ber, measured  on  the  side,  1.12 ;  depth  of  the  apertural  sinus,  .18.  Siphon  cylindrical, 
.07  inch  in  diameter,  where  the  septa  are  at  the  same  distance  apart. 

GYROCERAS  H.  de  Meyer. 
Gyroceras  Bannister!  W.  and  M. 

Shell  consisting  of  about  one  and  a  half  whorls,  barely  in  contact,  gradually  increasing 
in  diameter;  transverse  section  nearly  circular;  surface  ornamented  by  encircling  convex 
ridges  which  extend  quite  around  the  shell,  crossing  the  ventral  side  at  right  angles,  thence 
arching  backwards  to  the  dorsal  side,  where  the  corresponding  branches  meet  in  a  broadly 


NIAGAEA   LIMESTONE   OF    CHICAGO,  ILLINOIS.  103 

rounded  angle  of  about  100°.  The  distance  from  the  summit  of  one  ridge  to  that  of  the 
next,  measured  on  the  dorsum,  varies  from  one  third  the  transverse  diameter  of  the  whorl, 
to  considerably  less.  The  space  between  the  ridges  is  nearly  flat,  and  in  the  cast — but 
not  on  the  shell  —  discloses  indications  of  two  low,  barely  perceptible  ridges.  The  last 
chamber  seems  to  be  entirely  destitute  of  surface  ornaments,  except  incremental  lines, 
which  are  sinuate  dorsally,  to  correspond  with  the  ridges.  There  are  indications  that  the 
aperture  was  correspondingly  sinuate.  The  position  of  the  siphon  has  not  been  observed, 
but  a  feeble  depressed  line  or  shallow  furrow  runs  along  the  back  of  the  cast,  visible  be- 
tween the  ridges,  and  creating  a  suspicion  that  the  siphon  is  in  close  proximity. 

Dorso-ventral  diameter,  .78  inch  at  a  place  where  the  transverse  diameter  is  .73  inch ; 
distance  between  the  ridges  on  the  dorsum,  at  the  same  place,  .25  inch.  In  other  specimens 
the  ridges  are  more  approximated. 

This  species  differs  from  Gyroceras  (Litnites)  americanum  Billings,  in  not  being  flattened 
on  the  back,  and  in  the  course  of  the  annulations.  It  differs  from  Lituites  giganteus  Sower- 
by,  in  having  the  annulations  extend  quite  across  the  back  without  any  diminution  in  size. 

Named  in  recognition  of  aid  received  from  Henry  Bannister,  a  zealous  and  promising 
young  geologist  of  Evanston,  Illinois. 

LICHAS  Dalman. 

Lichas  pugiiax  W.  and  M. 

Plate  III.  figure  10. 

Body  large,  outlines  unknown.  Glabella  somewhat  parabolic  in  contour,  prominent,  with 
a  middle  lobe  and  two  lateral  ones  on  each  side.  Middle  lobe  consisting  of  two  regions, 
the  anterior  of  which  has  a  triangularly  rounded  base,  and  in  the  centre  is  extremely  prom- 
inent, the  front  margin  descending  precipitously  to  the  border ;  the  posterior  region  is  de- 
pressed and  cuneately  produced  backward  between  the  lateral  lobes,  diminishing  in  the  nar- 
rowest part  to  one  fifth  the  greatest  transverse  diameter  of  the  anterior  region,  and  then 
widening  behind  the  approximated  ends  of  the  lateral  lobes.  The  lateral  lobes  are  oblong- 
elliptic,  slightly  flattened  on  the  outer  side  by  the  eyes,  less  prominent  than  the  middle  lobe 
and  separated  from  it  by  deep  valleys ;  these  lobes  are  twice  as  long  as  broad,  and  their  lon- 
gitudinal axes  lie  at  an  angle  of  36°  with  the  axis  of  the  middle  lobe.  The  ocular  lobes 
are  smaller  and  more  depressed  than  the  last,  and  lie  against  their  outer  sides  a  little  pos- 
terior to  their  middle,  being  deeply  separated  from  them.  The  border  is  thick  and  narrow, 
regularly  curving  around  the  middle  lobe  of  the  glabella,  and  is  not  produced  in  front  into 
a  proboscis.  Occipital  ring  very  prominent  and  broad ;  furrow  deep.  All  parts  of  the 
glabella  are  covered  by  a  granular  crust. 

The  thorax  is  imperfectly  known.  It  appears  from  some  specimens  that  the  axis  is  prom- 
inent, and  from  numerous  others  that  the  lateral  lobes  are  broadly  expanded  and  im- 
perfectly articulated,  though  the  crust  covering  the  pleurae  is  deeply  furrowed  between  the 
joints  as  well  as  along  the  middle  of  each  pleura.  Some  of  the  articulations,  undoubt- 
edly posterior  ones,  become  very  broad  and  flat.  Every  portion  of  the  thorax  seems  to 
have  been  covered  with  a  separable,  coarsely  and  unequally  granulated  crust,  the  granules 
or  eminences  of  which  are  directed  backwards,  as  in  other  species  of  the  genus.  The  basis 
of  the  crust  is  marked  by  irregularly  wavy,  somewhat  continuous,  imbricated  furrows, 
which  seem  to  run  nearly  parallel  with  the  general  outline  of  the  body. 


104  WINCHELL   AND  MARCY  ON   FOSSILS   FROM  THE 

The  pygidiuiin  is  also  imperfectly  known.  It  consists  of  at  least  three  joints.  The  axis 
is  moderately  elevated  anteriorly;  the  first  two  segments  are  narrow,  the  third  much  wider, 
and  its  depressed  and  narrowed  posterior  portion  extends  apparently  to  the  caudal  extrem- 
ity. The  flattened  and  expanded  pleurae  are  surmounted  each  by  a  pair  of  broad,  elongated, 
obtusely  terminated,  pad-like  elevations,  which  terminate  much  short  of  the  tips  of  the 
pleurae.  In  two  large  specimens  these  elevations  are  separated  from  each  other,  and  from 
contiguous  pairs,  by  an  intervening  flat  area.  The  basis  of  the  granular  crust  is  marked, 
as  in  the  thorax,  by  concentric  imbricating  wrinkles.  Characters  of  the  margin  unknown. 

Length  of  cephalic  shield  to  the  collar,  1.8  inch ;  greatest  width  of  anterior  region  of 
middle  lobe,  1.0  inch;  length  of  lateral  lobe,  1.0;  width  of  lateral  lobe  of  thorax,  more  than 
two  inches ;  length  of  pygidium,  more  than  three  inches.  These  parts  may  belong  to 
different  individuals. 

We  at  first  imagined  the  conspicuous  and  unique  fragments  of  this  .large  species  to  belong 
to  L.  Nereus  Hall,  which,  in  a  general  way,  it  strongly  resembles.  It  may  be  distinguished 
by  the  absence  of  a  "proboscis,"  and  the  want  of  articulations  in  the  peripheral  area  of  the 
caudal  shield.  A  pygidium,  with  a  similar  flat  inarticulated  flap,  is  seen  in  Lichas  canadensis 
Logan,  (Can.  Eep.  1844,  p.  54). 

Lichas  decipiens  W.  and  M. 
Plate  III.  figure  11. 

Pygidium  semi-elliptic,  of  three  articulations,  with  a  prominent  axis  and  a  flat  border. 
Two  anterior  joints  of  axis,  narrow ;  posterior  consisting  of  an  anterior  narrower  portion 
and  a  posterior  depressed  portion,  rapidly  subsiding  to  a  level  with  the  lateral  lobes,  and 
tapering  to  a  point  before  attaining  the  caudal  extremity.  The  ribs  are  broad,  flattened, 
expanding,  divided  by  a  median  groove,  and  terminating  in  short  free  points.  The  anterior 
rib  is  nearly  transverse  at  its  origin,  and  distinctly  curves  backward.  The  second  makes  an 
angle  of  45°  with  the  axis  and  is  less  curved.  The  third  is  straight,  and  its  posterior  lobe 
or  moiety  is  parallel  with  the  axis,  meeting  the  corresponding  moiety  of  the  posterior  rib 
of  the  opposite  side.  The  surface  is  densely  granulated. 

Length  of  pygidium,  .5  inch ;  width,  .6  inch. 

BRONTEUS  Goldfuss. 

Bronteus  occasus  W.  and  M. 

Plate  III.  figure  12. 

Pygidium  with  the  axis  consisting  of  two  articulations.  The  limb  slopes  laterally  and 
posteriorly,  and  is  marked  by  seven  equal  ridges  radiating  on  each  side  from  the  axis,  and 
one  additional  on  the  median  line,  all  becoming  confluent  around  the  border.  These 
ridges,  or  rays,  exhibit  but  very  little  curvature.  The  median  (or  posterior)  ridge  is  nearly 
twice  as  broad  as  the  others ;  the  extreme  ridges  on  the  right  and  left  are  at  right  angles 
with  the  axis.  The  general  outline  is  parabolic.  Neither  striae  nor  granulations  are  ap- 
parent. 

Length,  .48  inch ;  breadth,  .62  ;  length  of  axis,  .13 ;  breadth  of  axis,  .23  inch. 

Several  small  pygidia  in  our  collection,  very  well  preserved,  appear  to  be  distinct  from 
any  described  species  known  to  us.  They  differ  from  B.  flabellifer  Goldf.  which  has  been 


NIAGARA   LIMESTONE   OF   CHICAGO,   ILLINOIS.  105 

doubtfully  identified  in  Canada,  by  their  straight  ribs,  not  reaching  the  margin,  and  by  the 
absence  of  strias  and  granulations.  The  species  is  quite  distinct,  of  course,  from  B.  niaga- 
rcnsis  Hall  (Pal.  N.  Y.,  II.  314,  pi.  Ixx.  3). 

ILUEXUS  Dalman.     BUMASTUS  Murchison. 

Ultonus  (Bumastus)  worthenanus  W.  and  M. 

Plate  III.  figure  13. 

Head  elevated,  greatly  inflated,  the  glabella  closely  imitating  the  superior  portions  of  the 
human  cranium  from  the  middle  of  the  forehead  over  to  the  lamboidal  suture.  The  lat- 
eral lobes  are  separated  from  the  glabella  by  shallow  furrows  which  arise  from  pits  on  the 
antero-lateral  aspects,  a  little  above  the  border,  and  arch  upwards,  backwards,  and  down- 
wards nearly  in  a  circular  arc  of  160°.  The  eyes  are  small,  superficially  elongate-elliptic, 
bent  over  the  most  prominent  portion  of  the  lateral  lobes  in  such  position  as  to  look  exactly 
at  right  angles  to  the  vertical  plane  passing  longitudinally  through  the  middle  of  the  ani- 
mal. Their  position  is  greatly  posterior  to,  and  a  little  below,  the  middle  of  the  head. 
The  facial  suture  starts  in  the  border,  below  the  antero-lateral  pit,  rises  with  slight  curva- 
ture, at  an  angle  of  45°  to  the  anterior  extremity  of  the  eye,  and  thence  descends  rapidly 
to  the  posterior  border.  The  fixed  cheek  has  thus  a  lunate  form.  The  movable  cheek  is 
limited  in  extent,  its  width  being  about  equal  to  the  length  of  the  eye  ;  it  extends  back- 
ward as  far  as  the  main  lobe  of  the  glabella.  The  occipital  ring  is  extremely  arched,  giv- 
ing the  head  a  truncate  appearance  posteriorly. 

In  young  specimens  the  glabella  is  relatively  more  depressed, — the  eye  being  halfway 
up  ;  the  eye  itself  is  more  prominent,  with  a  sub-ocular  furrow. 

The  hypostome,  in  a  young  specimen,  is  nearly  as  convex  as  the  glabella.  It  has  the 
form  of  a  pentagon  with  the  two  sides  opposite  the  base  rounded  and  coalesced  into  a  semi- 
circle,—  the  curved  side  of  the  figure  being  anterior,  the  base  posterior  and  transverse  to 
the  animal's  body.  The  two  sides  adjacent  to  the  base  are  deeply  isolated  from  the  cen- 
tral area  by  furrows  which  begin  at  the  lateral  angles  of  the  pentagon  and  extend  to  the 
base,  in  close  proximity  to  the  basal  angles.  The  thorax  is  unknown. 

The  pygidium  is  the  figure  included  in  the  arcs  of  two  circles,  the  anterior  of  which  is  of 
greater  radius,  and  embraces  about  60° — the  posterior  embracing  about  160.°  A  belt  around 
the  margin  is  somewhat  depressed,  but  no  trace  of  trilobation  is  apparent. 

No  portion  of  the  test  is  preserved  in  any  of  our  numerous  specimens  ;  and  the  casts  do 
not  exhibit  any  traces  of  superficial  ornamentation.  The  head  of  the  largest  individual  is 
1.9  inches  long,  2.2  broad,  and  1.4  high.  The  narrowest  part  of  the  glabella,  which  is 
between  the  eyes,  is  1.15  inches  across,  and  the  widest  part — the  front — 1.45  inches  across, 
the  width  next  the  collar  being  very  nearly  the  same. 

This  striking  species  might,  on  casual  comparison,  be  referred  to  Bumastus  larriensis  Mur- 
chison, but  on  extended  consideration  we  have  been  induced  to  regard  it  as  decidedly  dis- 
tinct from  the  types  of  that  species.  On  the  side  view  of  the  head  the  anterior  portion  Is 
more  depressed;  the  eye  is  below  the  middle  instead  of  above  it;  it  is  horizontal  instead  of 
oblique  ;  and  the  facial  suture,  instead  of  ascending  almost  vertically,  rises  at  an  angle  of 
45°.  On  the  view  from  above,  the  head  is  relatively  longer  and  narrower,  and  the  furrows 
isolating  the  glabella  much  more  distinct.  Moreover,  the  pygidium  of  B.  barriensis  (aut 
redius  larrensis)  is  more  than  a  semicircle, — in  our  species  considerably  less ;  it  is  also  much 
more  depressed,  and  its  border  is  flattened. 


106  WINCIIELL  AXD  MARCY   ON    FOSSILS   FROM   TIIF, 

We  hesitate  to  insist  upon  these  distinctions  after  the  foreign  species  has  been  recognized 
in  this  group,  in  New  York,  by  Prof.  Hull.  But  without  expressing  any  opinion  of  that 
identification  we  may  say  that  the  head  of  our  species  is  much  narrower  relatively  than 
that  figured  by  Hall,  and  the  glabella  has  a  greater  development  posterior  to  the  line  of 
the  eyes.  Some  of  the  pygidia  of  Hall's  species  greatly  resemble  ours, —  e.  g.  Plate  60,  fig. 
2,  Pal.  N.  Y.,  Vol.  II.  This  species  should  also  be  compared  with  Jllcenus  imperator  Hall, 
(Wis.  Geol.  Rep.  1861,  p.  49,)  from  the  Racine  limestone. 

ACIDASPIS  Murchison. 

Acidaspis  Ida  W.  and  M. 

Plate  III.  figure  13. 


o 


Head  more  than  twice  as  broad  as  long,  transversely  subelliptic  in  outline,  very  tumid. 
Glabella  consisting  of  a  median  body  and  three  lateral  lobes  on  each  side.  The  median 
body  is  twice  as  long  as  broad,  and  narrows  somewhat  in  front  of  the  anterior  lateral  lobes. 
It  rises  in  a  steep  arch  anteriorly  and  posteriorly,  being  somewhat  flattened  in  the  middle. 
A  slight  protuberance  is  generally  visible  in  the  middle  between  the  anterior  lateral  lobes. 
The  median  body  is  separated  from  the  lateral  lobes  by  shallow  "  false  furrows,"  uniting  the 
extremities  of  the  lateral  furrows  which  sink  into  deep  pits  between  the  lateral  lobes. 
The  dorsal  furrow  is  extremely  shallow  and  indistinct,  so  that  the  lateral  lobes  are  nearly 
confluent  with  the  fixed  cheeks.  The1  middle  pair  of  these  lobes  are  about  twice  the  size  of 
the  others ;  and  the  anterior  are  smaller  than  the  posterior.  Occipital  furrow  deep,  its  late- 
ral bifurcations  sinking  into  deep  pits  and  isolating  the  posterior  lateral  lobes.  Occipital 
ring  with  a  pair  of  slender,  slightly  diverging  spines,  gently  curved  downward  toward  the 
extremity,  and  having  a  length  of  about  one  inch.  Between  the  bases  of  the  spines  is  a 
small  tubercle  which,  in  good  specimens,  is  seen  to  become  a  short  erect  spine. 

The  fixed  cheek  is  convex,  somewhat  pyriform  in  outline. 

The  ocular  fillet  is  well  defined  along  the  antero-lateral  border  of  the  fixed  cheek  as  far 
as  the  eye,  which  is  situated  upon  a  slender,  diverging  peduncle,  about  three  tenths  of  an 
inch  high,  arising  opposite  the  middle  of  the  cheek. 

The  movable  cheek  is  broadly  crescentiform,  of  medium  size,  about  as  broad  as  the  main 
lobe  of  the  glabella,  projecting  forward  a  little  further  than  the  frontal  border.  Its  plane 
in  the  broadest  part  makes,  with  a  vertical  plane  through  the  axis  of  the  animal,  an  inferior 
angle  of  about  35°,  but  anteriorly  to  this  the  border  is  turned  upwards,  giving  a  concave 
upper  surface  to  that  part  of  the  cheek.  The  anterior  border  is  thickened  and  ornamented 
with  numerous  small  tubercles  arranged  at  regular  distances  ;  the  posterior  angle  is  drawn 
out,  and  terminates  in  a  slender  spine  about  one  inch  in  length  and  standing  at  an  angle  of 
55°  with  the  axis  of  the  animal.  The  inner  side  of  the  base  of  the  spine  is  continued  so 
far  as  to  deeply  indent  the  posterior  border. 

The  entire  surface,  except  the  occipital  ring,  is  covered  with  granules  of  unequal  size. 

Nothing  is  known  of  the  other  parts  of  the  animal,  except  that  a  fragment,  probably 
the  border  of  the  pygidium,  is  armed  with  short,  stout  spines. 

Transverse  diameter  of  cephalic  shield  (in  a  straight  line),  1.65  inches  ;  longitudinal  diame- 
ter, .87  ;  width  of  median  body  of  the  glabella,  .46 ;  width  of  fixed  cheek,  .25 ;  width  of 
movable  cheek,  .31;  middle  of  glabella  elevated  above  outer  border  of  movable  cheeks,  .36 
inch. 


NIAGARA  LIMESTONE   OF    CHICAGO,   ILLINOIS.  107 

We  are  in  possession  of  over  a  dozen  cephalic  shields  of  this  species,  and  they  all  agree 
to  a  remarkable  extent. 

This  fine  species  is  in  no  danger  of  being  confounded  with  any  other  American  form. 
It  has  close  analogues,  however,  in  A.  vcsiculosa  Bey  rich  (Barrande,  Silur.  Syst.  p.  715,  PL 
38,  figs.  13-21),  and  A.  Verneuilli,  (Id.  PI.  38,  figs.  1-9).  The  occipital  and  genal  spines, 
nevertheless,  are  longer,  the  ocular  peduncle  is  more  elevated  and  more  cylindrical,  (in  this 
resemblin^  A.  mira.)  the  lateral  lobes  are  more  confluent  with  the  cheeks ;  the  movable 
cheeks  are  more  depressed,  and  the  whole  head  is  transversely  more  elongate. 

Besides  the  foregoing  species  in  our  collection  from  this  interesting  locality,  the  following 
described  species  have  not  been  met  with  by  us. 

Bucania  chicagoensis  McChesney,  New  Paleozoic  Fossils,  p.  69. 

"       crassolaris  "  "  "  "       p.  91. 

"      -pervohita  "  "  "  "        p.  91. 

Orthoceras  cameolare  "  "  "  '•'       p.  93. 

"          stricelinealum     "  "  "  "        p.  94. 

Besides  the  organic  remains  already  enumerated,  we  are  in  possession  of  a  few  others 
in  a  condition  too  imperfect  for  determination ;  among  which  may  be  mentioned  specimens 
resembling  StropJiomena  and  Naticopsis  •  a  cluster  of  eight  or  ten  small,  hollow  conical,  slight- 
ly bent  tubes,  having  the  appearance  of  a  small  Dentalium ;  also  a  considerable  mass  of 
small  stellate  and  acicular  crystal-like  bodies,  resembling  freshly  fallen  snow-flakes,  which 
may  have  had  an  organic  origin. 

DECEMBER  22,  1864.  

SUPPLEMENTARY  NOTE. 

About  a  month  after  the  foregoing  paper  had  been  accepted  for  publication,  a  pamphlet 
appeared,  from  the  pen  of  Professor  James  Hall,  entitled,  "  Account  of  some  netv  or  little  knoivn 
Species  of  Fossils  from  the  Niagara  Group."  This  pamphlet,  while  mainly  devoted  to  fossils 
from  Wisconsin,  embraces  a  notice  of  twenty-two  species  of  fossils  from  Illinois,  most  of 
which  are  referred  to  Bridgeport,  and  the  remainder  of  which,  as  I  have  since  learned  from 
examinations  kindly  permitted  by  Prof.  Hall,  come  also  from  that  locality.  Of  these,  only 
eleven  species  are  quoted  from  Bridgeport} 

We  had  been  aware,  early  in  December,  1864,  that  Prof.  Hall  was  at  work  upon  fossils 
from  the  Niagara  group  of  Wisconsin  ;  and  one  of  us  also  informed  him  that  we  had  just 
completed  a  monograph  of  the  fossils  of  Bridgeport,  —  a  work  which  had  been  in  progress 
for  about  two  years.  It  did  not  occur  to  either  of  us  that  Prof.  Hall's  plan,  as  we  under- 
stood it,  would  embrace  fossils  recognized  only  at  the  locality  upon  which  we  had  been 
especially  engaged.  From  this  misunderstanding  has  resulted  a  little  synonymy  and  a  little 
clashing  of  identifications.  A  brief  review  of  Prof.  Hall's  paper  seems,  consequently,  to  be 
called  for. 

1.  The  following  twelve  species  are  quoted  by  Prof.  Hall  from  Bridgeport,  and  other  local- 
ities. 

Jllcenus  insignis,  I.  armatus,  Sphcerexochus  minis  Beyrich ;  Amboni/chia  Aphcea,  Avicula  undata, 
Avicula  emacerata,  Conrad ;  Cypricardinia  arata,  Modiolopsis  Dictceus,  Modiolopsis  rectus,  Modiobp- 
sis  subalatus,  Amphiccelia  Leidyi,  Subulites  ventricosus. 

1  The  locality  of  Plerinea  Brisa  Hall,  is  not  given,  but  it  is  now  known  to  be  from  Bridgeport. 


108  WINCIIELL   AND   MARCY   ON    FOSSILS    FROM  THE 

2.  The  following  eleven  species  are  quoted  only  from  Bridgeport. 

IcWvjocrinus  subanguhris,  Illcenus  armatns,  Acidaspis  Danai,  Lichas  brcviceps  (?),  Ambonychia 
acutirostris,  Pterinea  Brisa,  Cypricardites  (?)  quadrilatera,  Pleurotomaria  Avion,  Tremanotus  Alpheus, 
Cyrtoceras  Fosieri,  Gomphoceras  scrinium. 

3.  The  following  three  species,  quoted  from  Bridgeport,  have  not  yet  been  seen  there  by  us. 
Sph&rexochus  minis  Beyr.,  Modiolopsis  Dictccus,  Cypricardites  (?)  quadrilatera. 

4.  The  following  five  species,  described  by  us  as  new,  have  been  identified  by  Hall  Avith 
old  species. 

(a)  IcJdhyocrinus  corlis  W.  and  M.,  with  I.  subangularis  Hall.     Besides  the  uniform  want  of 
angularity  of  this  species,  it  differs  in  the  perfectly  straight  bounding  lines  of  the  upper 
and  lower  sides  of  the  secondary  and  tertiary  radials,  which,  in  I.  subangularis,  are  bounded 
by  a  double  curvature,  as  in  I.  Icevis.     We  are  not  in  possession  of  specimens  of  I.  suban- 
gularis showing  the  form  of  the  primary  radials,  but  Hall  states  that  "  the  centres  of  the 
upper  margins  are  depressed  or  emarginate,  and  their  lower  margins  produced."     Scores 
of  specimens  of  I.  corlis  show  a  uniform  difference  in  this  respect,  not  to  speak  of  the 
supposed  difference  of  basal  structure. 

(b)  Lichas  pugnax  W.  and  M.,  with  L.  breviceps?  Hall.     The  glabella  is  extremely  similar 
to  that  of  L.  breviceps,  but  the  pygidium  has  its  axis  much  narrower  anteriorly,  and  it 
continually  tapers  backwards  instead  of  widening.     The  plurae  also  differ. 

(c)  Pterinea  volam  W.  and  M.,  with  Avicula  emacerata  Conrad.     Had  Prof.  Hall  seen  the 
full-grown  and  perfect  specimens  in  our  possession,  it  is  doubtful  whether  this  identification 
would  have  been  made. 

(d)  Subulitcs  brevis  W.  and  M.,  with  S.  vcntricosus  Hall.    We  are  not  confident  in  our  opinion 
in  this  case,  but,  besides  the  contrast  in  proportions,  already  pointed  out,  it  may  be  stated 
that  all  the  specimens  in  our  possession  (as  well  as  Prof.  Hall's)  have  the  upper  part  of  the 
spire  turned  to  one  side. 

5.  The  following  six  new  genera  and  species,  described  by  Prof.  Hall,  have  been  iden- 
tified by  us  with  established  forms. 

(a)  Ambonychia  Aphcea,  with  A.  mytiloidea  Hall.    Prof.  Hall  has  cited  also  A.  acutirostra  Hall, 
from  Bridgeport,  and  refers  to  his  Ann.  Rep.  of  Progress  of  Geol.  Sttrv.  of  Wisconsin  for  1860. 
Our  copy  of  that  Report  (embracing  a  manuscript  copy  of  a  "galley"  of  matter  not  bound 
up  with  the  Report),  contains  no  mention  of  A.  acutirostra,  or  any  other  Niagara  species  of 
that  genus,  except  A.  mytiloidea.     The  same  is  true  of  the  final  Report  for  1862.     Both  A. 
Aphcea,  and  A.  acutirostra  must  be  extremely  near  to  A.  mytiloidea,  —  judging  from  the 
descriptions ;  and  it  is  probable  that  our  identifications,  however  correct,  have  embraced 
both  the  forms  separated  by  Prof.  Hall.  , 

(b)  Pterinea  brisa   Hall,  is   undoubtedly  Ambonychia   stricecosta   McChesney,  or  Pterinea 
stricecosta  W.  and  M. 

(c)  Amphiccelia  Leidyi  Hall,  is  Ambonychia  neglecta  McChesney,  or  Pterinea  neglecta  W.  and  M. 
This  new  sub-genus  (of  Lcptodomus,  as  supposed)  will  hardly  stand,  as  our  abundant  materials 
have  shown  that  the  species  on  which  it  is  founded  possesses  a  long,  broad  striated  carti- 
lage plate,  —  an  important  character  not  seen  by  Prof.  Hall,  and  one  which,  with  the 
cardinal  teeth,  make  it  a  proper  Pterinea.     At  least,  it  cannot  stand  as  a  subgenus  of  Lep- 
todomus.    At  the  same  time  the  general  form  departs  considerably  from  the  type  of  Pterinea 
(P.  Icevis  Goldf.)  in  being  less  modified  by  the  anterior  and  posterior  relations.     The  deep 
triangular  pit  beneath  the  break  in  each  valve,  and  the  duplex,  crescentic  posterior  muscu- 


NIAGARA   LIMESTONE   OF    CHICAGO,   ILLINOIS.  109 

lar  scar  may  also  be  cited  as  furnishing  some  grounds  for  a  subgeneric  distinction  under 
Pterinea.  This  form  may  be  compared  with  Avicula  Triton  Salter  (Mem.  Geol.  Surv.  Great 
Brit.  Vol.  II.  Pt.  I.  PI.  xxiii.  fig.  5.) 

(d)  Pleurotomaria  Axion  Hall,  has  been  referred  by  us  to  P.  Hold  Hall.     We  have,  how- 
ever, in  our  notice,  cited  the  disagreements,  while,  in  the  absence  of  authentic  specimens 
of  P.  Halei,  we  hesitated  to  found  a  new  species  on  the  Bridgeport  specimens.     Having 
now  seen  Prof.  Hall's  types  of  that  species,  —  an  opportunity  for  which  we  would  again 
express  our  obligations,  —  we  are  convinced  that  the  separation  of  the  Bridgeport  speci- 
mens is  perfectly  proper. 

(e)  Tremanotus  Hall,  is  a  new  subgenus  of  Porcettia,  founded  upon  our  Bellerophon  (Bucania) 
perforatus.     We  may  have  sufficient  evidence  of  the  existence  of  dorsal  perforations  in 
this  species.    Nevertheless,  the  perfectly  symmetrical  enrollment  of  even  the  young  shell, 
as  well  as  the  enormously  expanded  aperture  (not  seen  by  Hall),  would  seem  to  indicate 
stronger  affinities  with  Bellerophon  than  with  Porcellia. 

6.  The  following  five  new  species  described  by  us,  have  been  also  described  by  Hall. 

Ittcenus  worthenanus  W.  and  M.  (I.  insignis  Hall).  Acidaspis  Ida  W.  and  M.  (A.  Danai 
Hall).  Clidophorus  macchesneyanus  W.  and  M.  (Modiolopsis  rectus  Hall).  Bellerophon  (Bucania) 
perforatus  W.  and  M.  (Tremanotus  Alpheus  Hall).  Gomphoceras  Marcyce  W.  and  M.  (Gom- 
phoceras scrinium  Hall).  . 

Of  these,  the  following  are  quoted  only  from  Bridgeport :  Acidaspis  Danai,  Tremanotus 
Alpheus,  Gomphoceras  scrinium. 

Illcenus  armatus  Hall,  has  been  detected  among  our  specimens  since  the  appearance  of 
Prof.  Hall's  paper. 

Ct/pricardinia  arata  Hall,  has  also  more  recently  been  observed. 

Avicula  undata  Hall.  Specimens  have  been  brought  to  light  which  resemble  this  species, 
and  it  is  probable  that  they  are  the  forms  referred  to  it  by  Hall.  They  differ,  however,  in 
having  the  beak  su-bterminal,  and  the  posterior  wing  not  isolated  from  the  body  of  the 
shell  and  not  extending  as  far  back  as  the  most  projecting  part.  The  right  valve  has  two 
posterior,  linear,  diverging  teeth,  which  terminate  abruptly  three  fifths  the  distance  from 
the  beak  to  the  cardinal  extremity.  We  should  feel  inclined  to  separate  these  forms  from 
A.  undata  Hall.  For  the  present  we  designate  them  as  Pterinea  undata  Hall,  sp. 

Modiolapsis  subalata?  Hall.  We  adopt  nearly  the  same  observations  in  reference  to 
certain  other  forms,  which  probably  are  the  ones  referred  by  Hall  to  Modiolopsis  subalata. 
Our  specimens,  however,  have,  in  the  right  valve,  two  linear,  posterior  teeth,  and  two  short 
lamelliform  anterior  teeth.  The  size  of  the  shell  is  also  more  than  twice  that  of  the 
types  of  the  species.  It  seems  to  possess  the  characters  of  a  true  Pterinea.  The  left  valve 
is  much  more  ventricose,  and  shows  distinctly  a  strong  arcuation  of  the  body,  which  is 
less  visible  in  the  thinner  right  valve.  Casts  of  both  valves  show  a  few  obscure,  remote 
radiating  ridges  on  the  anterior  slope. 

The  following  new  species  have  also  been  brought  to  light  by  recent  work  in  the 
quarry :  — 

8 


110  WINCHELL   AND   MARCY   ON   FOSSILS   FROM   THE 

Megistocrinus  necis  W.  and  M. 
Plate  II.  figure  6. 

Body  of  medium  size,  pentangularly  ovoid,  tapering  below  and  contracted  toward  the 
bases  of  the  arms,  giving  the  greatest  diameter  a  little  above  the  middle ;  flattened  along 
the  interradial  spaces,  causing  the  rays  to  occupy  five  conspicuous  angles.  The  inter- 
brachial  spaces  are  also  flattened.  Basals  rather  small,  hexagonal.  First  radials  the 
largest  plates  of  the  body,  hexagonal  or  heptagonal,  one  third  higher  than  wide,  the  lower 
lateral  sides  much  the  longest.  Second  radials  smaller,  hexagonal,  similar  in  form  to  the 
first  radials ;  third  radials  heptagonal,  in  some  specimens  nearly  twice  as  long  as  wide, 
supporting  on  its  two  short  upper  sides  a  pair  of  hexagonal  supraradials,  above  each  of 
which  is  a  second.  Regular  interradials  about  ten  ;  the  first  a  little  smaller  than  the  first 
radial,  hexagonal,  approximately  equilateral,  surmounted  by  a  pair  of  smaller  plates,  and 
these  by  a  pair  still  smaller,  the  others  diminishing  similarly  in  size  upwards.  First  azygos 
interradial  heptagonal,  a  little  smaller  than  the  antero-lateral  first  radials,  supporting  three 
variable  plates  in  the  second  series,  of  which  the  middle  one  is  much  the  smallest.  The 
remaining  ones  gradually  smaller,  amounting  apparently  to  twenty  or  more  in  number. 

The  forms  and  arrangement  of  the  plates  in  this  species  are  quite  similar  to  those  of  M. 
Christyi  Hall  sp.  The  bifurcation  of  the  rays,  however,  is  considerably  lower.  The  form 
of  the  cup,  moreover,  is  very  different,  being  somewhat  obpyramidal  below,  instead  of 
urn-shaped,  while  it  is  also  much  contracted  above.  The  angulations  along  the  rays  modify 
the  form  of  the  cup,  and  are  not  to  be  compared  with  the  small  threadlike  ridges  occupy- 
ing the  same  position  in  the  Waldron  species.  The  specimens  show  constant  characters. 

Megistocrinus  infelix  W.  and  M. 
Plate  II.  figure  7. 

Body  of  moderate  size,  urn-shaped,  having  a  rounded  base,  but  slightly  diverging  sides, 
and  no  constriction  below  the  arm  bases,  which  are  somewhat  prominent.  Raised  ridges 
extend  from  the  basals  over  the  radials,  supraradials,  and  brachials.  Basals  rather  small,  as 
large  as  the  second  radials.  Radials  rapidly  decreasing  in  size  ;  first  radials  large,  nearly 
as  broad  as  long,  with  the  upper  side  the  shortest ;  second  radials  with  the  upper  and  lower 
sides  short ;  third  radials  oval,  heptagonal.  First  supraradials  regularly  hexagonal,  two 
thirds  as  large  as  the  third  radials ;  second  supraradials  similar  in  form,  but  smaller. 
Brachials  two  beneath  each  arm-base.  Arms  in  ten  pairs.  Regular  interradials  about 
ten  or  twelve  in  each  interradius;  the  first,  hexagonal,  as  large  as  the  second  radials 
or  larger ;  above  this  are  two  others  of  the  size  of  the  third  radials,  followed  by  about 
three  or  four  pairs  decreasing  in  size.  Azygos  interradials  apparently  thirty  or  more,  gen- 
erally hexagonal  in  form,  with  nearly  equal  sides. 

Dome  depressed,  nearly  flat,  composed  of  a  large  number  of  plates,  with  apparently  a 
central  proboscis.  The  dome  is  marked  by  ten  radiating  furrows,  increasing  in  depth  and 
width  from  the  centre  to  the  spaces  between  the  pairs  of  arms,  and  extending  a  short 
distance  down  the  side  of  the  cup,  where  they  vanish.  The  azygos  furrow  is  much  deeper, 
and  deeply  indents  the  upper  part  of  the  azygos  side  of  the  cup. 


NIAGARA   LIMESTONE    OF    CHICAGO,   ILLINOIS.  Ill 

This  species  has  the  calycinal  form  of  M.  Christyi  Hall  sp.,  but  in  that  species  the  bifurca- 
tion of  the  rays  takes  place  at  more  than  two  thirds  the  distance  from  the  stem  to  the  arm 
bases,  while  in  ours  the  bifurcation  is  very  little  above  the  mean  height  of  the  cup.  The 
marked  sulcations  between  the  pairs  of  arms,  especially  on  the  azygos  side,  —  existing  both 
on  the  exterior  and  in  the  cast,  —  constitute  the  most  marked  peculiarities  of  our  species  so 
far  as  at  present  known. 

Holocystites  sphsericus  W.  and  M. 

Body  spheroidal,  slightly  produced  on  the  basal  side,  composed  of  about  twelve  ranges  of 
polygonal  plates  rather  irregularly  disposed,  and  varying  both  in  form  and  size,  each  plate 
apparently  being  indented  in  the  middle. 

The  only  specimen  of  this  cystidean  in  our  possession,  is  a  mould  of  a  portion  of  the 
exterior,  which,  when  first  discovered,  was  nearly  a  hollow  hemisphere.  Its  generic  rela- 
tions are  not  satisfactorily  shown,  but  the  great  number  of  ranges  of  plates  seems  to  ally 
it  to  Holocystites,  —  a  genus  so  abundantly  represented  in  the  neighboring  State  of  Wis- 
consin, while  the  globoid  form  distinguishes  it  from  any  of  the  species  recently  described 
by  Prof.  Hall. 

Conocardium  ornatum  W.  and  M. 
Plate  II.  figure  15. 

Shell  small,  very  ventricose ;  beak  a  little  nearest  the  anterior  end,  projecting  beyond  the 
hinge  line  and  greatly  incurved ;  surface  arching  from  the  beak  to  the  ventral  side  in  nearly 
the  form  of  a  semicircle.  The  truncation,  or  separation  of  the  rostrate  slope  from  the 
anterior  aspect  of  the  shell  forms  a  posterior  angle  of  about  75°  with  the  cardinal  side,  and 
an  anterior  angle  of  about  55°  with  the  plane  separating  the  two  valves.  This  truncated 
plane  rises  into  a  crest  or  elevated  rib  on  the  surface  of  the  valve,  a  little  anterior  to  which 
and  forming  an  angle  of  about  20°  with  it,  is  another,  double-crested,  but  feebler  rib.  The 
remainder  of  the  surface  is  marked  by  regular  radiating  raised  striae.  Decussating  these 
and  the  ribs  is  a  set  of  numerous  sharp  raised  concentric  striae  stronger  than  the  radial 
ones,  the  two  sets  producing  a  beautifully  cancellated  surface.  The  concentric  striae  extend 
over  the  rostrate  slope  of  the  valve,  but  become  there  feebler,  more  crowded,  and  less 
rigid. 

Length  of  the  shell,  .41 ;  dorso-ventral  diameter,  .30 ;  thickness  through  both  valves, 
.32 ;  distance  from  beak  to  anterior  end,  .16 ;  to  rostrate  extremity,  .25  inch. 

Porcellia  senex  W.  and  M. 
Plate  III.  figure  6. 

Shell  small,  consisting  of  one  and  a  half  or  two  very  rapidly  enlarging,  detached  whorls, 
which  are  somewhat  oblique  in  the  young,  but  afterwards  continue  very  nearly  in  one 
plane.  Toward  the  aperture  the  shell  is  flattened  and  sub-nodulous  on  the  dorsum,  —  the 
nodes  consisting  of  a  larger  and  a  smaller,  alternating  with  each  other  in  a  line  along 
the  middle  of  the  flattened  surface.  The  angle  by  which  the  dorsal  surface  unites  with  the 
upper  side  of  the  whorl  is  rounded;  the  other  angle" is  considerably  sharper.  The  aperture 
is  not  expanded,  but  presents  a  deep  sinus  extending  across  the  dorsal  side.  Apex  of  spire 
depressed  much  below  the  level  of  the  upper  side  of  the  outer  whorl. 


112  WINCHELL  AND   MARCT  ON    FOSSILS  FROM   THE 

Greatest  diameter  of  shell,  .83 ;  transverse  diameter  of  whorl  at  aperture,  .36 ;  the  same 
one  inch  back,  .22 ;  dorso-ventral  diameter  at  aperture,  .30 ;  depth  of  sinus,  .22  inch. 

The  total  number  of  species  thus  far  known  from  the  locality  is  eighty-two.  Of  these 
thirty-nine  have  been  described  by  us,  thirty-nine  by  others,  and  four  are  not  specifically 
determined.  There  are,  besides,  three  others  referred  by  Hall  to  the  locality,  but  not 
seen  by  us. 

NOTE.  We  are  authorized  by  Prof.  Hall  to  state  that  he  relinquishes  all  claims  upon  our  two  species,  follow- 
ing, which  were  published  by  him  after  our  paper  had  been  read,  viz :  Gomphoceras  Marcyce,  and  Acidaspis  Ida. 
A  similar  announcement  is  to  be  made  in  a  postscript  to  his  paper,  on  the  appearance  of  the  completed  Report  of 
the  Regents  of  the  University  of  the  State  of  New  York,  vol.  xviii. 


EXPLANATION  OF  PLATE  II. 

PAGE 

Fio-.  l. — CLADOPORA  LICHENOIDES  "W.  and  M 84 

B 

View  of  a  portion  of  a  frond. 

la,  a,  a.     Ramose  prolongations  of  the  explanate  portion. 
16,  b.  Stumps  of  other  branches  broken  off. 

Fig.  2. — CLADOPORA  VERTICILLATA  W.  and  M 84 

View  of  one  of  the  verticils. 

la.  Place  of  supposed  accessory  stem. 

Fig.  3. — ISCHADITES  TESSELLATUS  W.  and  M 85 

Fior.  4. — ACTINOCRINUS  OBPYRAMIDALIS  W.  and  M '. 87 

o 

4a.  Base  of  left  postero-lateral  ray. 

46.  Base  of  right  antero-lateral  ray. 
Fig.  5. — MEGISTOCRINUS  MARCOUANUS  W.  and  M 87 

View  of  left  side  of  medium  sized  specimen. 
Fig.  6. — MEGISTOCRINUS  NECIS  W.  and  M 109 

6a.  Dorsal  side  of  a  small  specimen. 

66.  Outline  of  a  larger  specimen. 
Fig.  7. — MEGISTOCRINUS  INFELIX  W.  and  M 110 

la.  View  of  right  side. 

76.  View  of  dome,  showing  deep  sulcation  on  azygos  side. 
Fig.  8. — STROPHOMENA  MACRA  W.  and  M 91 

8a.  Exterior  of  ventral  valve. 

86.  Interior  of  same  valve  of  a  younger  specimen. 
Pig.  9. — STROPHOMENA  NIAGARENSIS  W.  and  M 92 

9a.  Cast  of  ventral  valve. 

96.  Cardinal  side  of  same. 
Fig.  10. — STRKPTORHYNCHUS  HEMIASTER  W.  and  M 92 

10a.  Exterior  of  cast  of  ventral  valve. 

106.  Area,  pseudo-deltidium  and  hinge-line. 
Fig.  11. — PENTAMKRUS  CHICAGOENSIS  W.  and  M 94 

Ha.  Front  view  of  ventral  valve. 

116.  Side  view  of  the  same. 
Fig.  12. — PTERINEA  REVOLUTA  W.  and  M 95 

Exterior  of  portion  of  right  valve. 
Fig.  13. — EDMONDIA  NILESI  W.  and  M 97 

13a.  Exterior  of  right  valve. 

136.  Cast  of  left  valve,  showing  muscular  impression. 

13c.  Hinge-line  of  cast  of  a  right  valve. 
Fig.  14. — CONOCARDIUM  NIAGAUENSE  "W.  and  M 97 


Memoirs  Boston  Soc. Nat. Hist. Vol.  f . 


Plate  2 


A.WincMl  del.  L.Trornrelot  on  ston«  . 

Winch  ell,  &  Marcy  on  tlie  Fossils  of  tlie  Nia 


J.EBufford  i  Co.  print. 

Limestone  at  Chicago,!!!. 


OF  THE 
UNIVERSITY  OF  ILLINOIS 


tlBPARY 
OF  THE 

UNIVERSITY  OF  ILLINOIS 


Memoirs  Boston  5oc.Nat.Hist.Yol.  I 


Plate  3 


A  TOndiell  del  L.Trouvelot  on  stone  +  J.H.Bnfford  i  Co  print. 

WrncHel}  &.Marcy  ontlie  Fossils  of  the  Niagara  Limestone  at  Chicago  JU. 


NIAGARA    LIMESTONE   OF    CHICAGO,  ILLINOIS.  113 

Fig.  15. — CONOCAKDIUM  ORNATUM  W.  and  M ^  .<<....  Ill 

Fig.  16. — PLATYCERAS  COMPLANATDM  W.  and  M 98 

16a.  View  of  upper  side. 

166.  View  of  aperture. 

Fig.  17. — HOLOPEA  NIAGAKENSIS  W.  and  M 99 

Fig.  18. — HOLOPEA  CHICAGOKNSIS  W.  and  M 99 

Fig.  19. — StJBULiTES  BREVIS  W.  and  M 99 

EXPLANATION  OF  PLATE  III. 

Fig.  1. — PTERINEA  SUBALATA  (Hall)  W.  and  M 109 

Cast  showing  linear  posterior  and  anterior  teeth. 
Fig.  2.— PTERIKEA  UNDATA  (Hall)  W.  and  M 109 

Cast  showing  linear  posterior  teeth. 
Fig.  3. — CLIDOPHORUS  MC  CHESNEYAKUS  W.  and  M 96 

Cast  of  left  valve  showing  clavicular  impression,  muscular  scar  and  pallial  outline. 
Fig.  4. — PLETTROTOMARIA  GONOPLEURA  W.  and  M 97 

Exterior  of  specimen  witli  a  defective  base. 
Fig.  5. — PLEUROTOMARIA  SIGARETOIDES  W.  and  M 98 

Cast,  defective  at  the  aperture. 
Fig.  6. — PORCELLIA  SENEX  W.  and  M Ill 

6a.  View  of  aperture  and  spire  of  a  cast. 

66.  Dorsum  of  same,  showing  notch  and  nodular  elevations. 
Fig.  7. — BELLEROPHON  (TREMANOTXJS)  PERFORATUS  W.  and  M 100 

la.  Cast,  with  apex  and  a  portion  of  aperture  broken  away. 

76.  Portion  of  exterior  of  a  specimen  from  near  the  aperture. 
Fig.  8. — GOMPHOCERAS  MARCYJE  W.  and  M 10 1 

8a.  Left  side  of  a  cast,  showing  the  faint  encircling  furrows,  and  an  outline  continuation  of  the 
specimen  to  near  the  apex,  as  demonstrated  in  specimens  actually  examined. 

86.  View  of  the  aperture  of  another  specimen. 

Sc.  Fragment,  showing  the  obliquely  moniliform  sub-ventral  siphon,  and  the  convexity  of  the  septa. 
Fig.  9. — LITUITES  HERCULES  W.  and  M 101 

Cast  of  a  medium-sized  specimen,  drawn  one  half  the  natural  size,  showing  chamber  of  habitation 
with  faint  encircling  furrows. 

This  is  not  a  representation  of  one  of  the  typical  specimens,  and  there  is  even  some  doubt  of  its 

specific  identity  with  them. 
Fig.  10. — LICHAS  PDGNAX  W.  and  M ; 102 

10a.  Cast  of  a  cephalic  shield. 

106.  Side  view  of  the  same. 

lOc.  Exterior  of  a  defective  pygidium. 
Fig.  11. — LICHAS  DECIPIENS  W.  and  M 103 

Cast  of  a  pygidium. 
Fig.  12. — BRONTEUS  OCCASUS  W.  and  M 104 

Cast  of  pygidium. 
Fig.  13. — ACIDASPIS  IDA  W.  and  M 105 

Cast  of  cephalic  shield,  with  spines  restored,  as  seen  in  numerous  specimens. 
9 


ERRATA. 

Page  93,  line  17  from  bottom,  for  "  Athyris"  read  "  Meristella." 

Page  99,  line  18  from  bottom,  for  «  figure  18  "  read  "  figure  17." 

Plate  II.  figure  2.  Cladopora  vertidllata.  The  engraver  has  omitted  the  "  a  "  which  should  stand  at  the  upper 
left  hand  side  at  the  semicircular  notch. 

Plate  II.  figure  15.  Oonocardium  ornatum.  The  engraver  has  omitted  the  delicate  radiating  lines  on  the  ante- 
rior side,  and  the  delicate  concentric  lines  of  the  rostrate  side. 

Plate  III.  figure  3.     Clidophorus  Me  Chesneyanus.     The  muscular  impression  has  been  omitted  in  the  engraving. 

Plate  III.  figure  11.  Lichas  decipiens.  The  outline  is  palpably  incorrect.  Moreover,  the  lines  separating  the 
articulations  of  the  lateral  lobes  do  not  exhibit  the  curvatures  noticed  in  the  description. 

Plate  III.  figure  13.  Acidaspis  Ida.  The  engraver  has  omitted  the  furrow  behind  the  ocular  filet  or  thread  on 
the  right  side. 


